Integrated button activation sensing and proximity sensing

ABSTRACT

Apparatuses and methods for coupling a group of sensor elements together in one mode to collectively measure a capacitance on the group of sensor elements, in addition to individually measuring a capacitance on each of the sensor elements in another mode. The touch-sensor buttons may be used individually for button-activation sensing, and the touch-sensor buttons may be used collectively for proximity detection. The touch-sensor buttons and a ground conductor that surrounds the touch-sensor buttons may also be collectively used for proximity detection. The apparatus may include a processing device, and a plurality of sensor elements that are individually coupled in a first mode for button-activation sensing and collectively coupled in a second mode for proximity sensing.

RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.60/910,405, filed Apr. 5, 2007.

TECHNICAL FIELD

This invention relates to the field of user interface devices and, inparticular, to touch-sensor devices.

BACKGROUND

Computing devices, such as notebook computers, personal data assistants(PDAs), kiosks, and mobile handsets, have user interface devices, whichare also known as human interface devices (HID). One such user interfacedevice is a touch panel having multiple buttons for controlling adevice, such as a touch panel of a television (TV), a video cassetterecorder (VCR), a digital video recorder (DVR), a digital video disc(DVD) player, a receiver, a computer, a radio, lights, fans, industrialequipment, or the like. For example, considering a standard consumerelectronics device like a DVD player, the DVD player front panel hasbuttons that form a user interface (UI). In general terms, a UI receivesinput from the user and allows the user to interact with an electronicdevice. Some UIs use traditional mechanical buttons and some newer UIsuse touch-sensor buttons (e.g., capacitance sensing buttons).

Capacitance sensing is used in wide variety of user interfaceapplications. Examples include touchpads on notebook computers,touchscreens, slider controls used for menu navigation in cellularphones, personal music players, and other hand held electronic devices.One type of capacitance touch-sensor device operates by way ofcapacitance sensing utilizing capacitive sensors. One way in which thecapacitance detected by a capacitive sensor changes is as a function ofthe proximity of a conductive object to the sensor. The conductiveobject can be, for example, a stylus or a user's finger. Thetouch-sensor devices may include single sensor elements or elementsarranged in multiple dimensions for detecting a presence of theconductive object on the touch-sensor device. Regardless of the method,usually an electrical signal representative of the capacitance detectedby each capacitive sensor is processed by a processing device, which inturn produces electrical or optical signals representative ofactivation, position, or the like of the conductive object in relationto the touch-sensor device, such as a touch panel. A touch-sensor strip,slider, or touchpad operates on the same capacitance-sensing principle.

Capacitance sensing has been implemented in a wide variety of electronicdevices to replace mechanical buttons in the electronic devices.Capacitance sensing has many advantages over conventional cursor controldevices, mechanical switches, and rotary encoders. A principal suchadvantage is the lack of moving parts, which allows capacitance sensingto provide great improvements in reliability since there are no movingparts to wear out.

Typically, a capacitance sensing system detects changes in capacitancebetween a sensing element and electrical ground. For example, in acapacitance sensing button, when the users'finger is in close proximityto the sensor element, a capacitance is formed between the sensorelement and the finger, and as the finger is effectively at a groundpotential, a detectable capacitance to ground is present when the user'sfinger is close to the sensor element. In a touchpad or slider, theposition of the user's finger is detected by measuring the difference incapacitance to ground between a number of sensing elements arranged asan array. The capacitance sensing system detects the presence of theuser's finger over a button area and registers a button press as aresult.

One type of conventional capacitance sensing touch panel 100, asillustrated in FIG. 1, includes eight touch-sensor buttons 101, whicheach include a sensor element 102. Surrounding each sensor element 102is a dielectric 103 (e.g., dielectric material or air) that separatesthe touch-sensor buttons 101 from a ground conductor 104 that isdisposed to surround the sensor elements 102. The change in capacitanceon the sensor element 102 resulting from the introduction of either aconductive object into close proximity to the sensor element 102 issensed. Electric field lines which run between conductive elements,namely the ground conductor 104 and the sensor element 102, through thedielectric 103 and the dielectric above and below the touch panel 100.When nothing changes (e.g., the configuration is static), a given sensorelement 102 has a fixed capacitance determined by the properties of theconductor, the dielectric, geometry of the assembly, environmentalconditions, as well as other factors. Introduction of a conductiveobject into close proximity to the sensor element 102 changes theenvironment, which consequently changes the capacitance of the sensorelement 102. For example, placing a finger in proximity to the sensorelement 102 raises the capacitance on sensor element 102. The increasein capacitance is registered by the capacitance sensing device as a“button press.”

In almost all button-press applications of capacitance sensing, theconductive elements (e.g., sensor elements 102 and ground conductor 104)are isolated from the user by a dielectric material as an overlay. Sincethe electric field penetrates the overlay, when the user's finger (orother conductive object) is in proximity to the sensor element 102, thecapacitance sensing device can detect a change in the capacitance. Itshould be noted that since the conductive elements are isolated by anoverlay, the sensor elements 102 are not actually touched by theconductive object. As such, sensor elements, such as sensor elements102, are considered to be proximity sense technology. However, in theproximity sense technology, the sensor element 102 may be a “capacitiveproximity sensor” or a “capacitive button sensor” (e.g., touch-sensorbutton). Whether a sensor element 102 is considered to be a capacitiveproximity sensor or a touch-sensor button is based on the sensitivity ofthe processing device, which processes the data from sensor element 102.The difference between a capacitive proximity sensor and a capacitivebutton sensor is that the proximity sensor is tuned to respond beforethe user touches the dielectric overlay and the button sensor is tunedto respond when the user actually touches the surface of the dielectricoverlay. As a result, a proximity sensor is usually tuned to be muchmore sensitive to a change in capacitance than capacitive buttonsensors. For technical reasons, standard engineering practice forcapacitive button sensors is to use a “ground” conductor 104 thatsurrounds the capacitive button 101.

Conventional UIs that implement both proximity sensing andbutton-activation sensing use a dedicated, discrete proximity sensor.The proximity sensor element is physically separate from the sensorelements required for capacitive button sensing. For example, the touchpanel 100, which includes both proximity sensing and button-activationsensing, requires an additional sensor element 106 to perform proximitysensing, as illustrated in FIG. 1B. The additional proximity sensorelement 106 is disposed around the perimeter of the touch panel 100, andis separated from the ground conductor 104 by a dielectric 105. Thecapacitive proximity sensor 106 is usually large due to the use model,since the desired use model for a proximity sensor is to detect when theuser's hand is in proximity to the area of the user interface (e.g.,touch panel 100), as opposed to touching the overlay of one of the touchsensor buttons. The capacitive proximity sensor 106 usually surroundsthe user interface.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is illustrated by way of example, and not by wayof limitation, in the figures of the accompanying drawings.

FIG. 1A illustrates a conventional touch panel having eight touch-sensorbuttons surrounded by a ground conductor.

FIG. 1B illustrates the conventional touch panel of FIG. 1 including anadditional proximity sensor element for proximity sensing.

FIG. 2 illustrates a block diagram of one embodiment of an electronicsystem having a processing device for detecting a presence of aconductive object.

FIG. 3A illustrates a varying capacitance sensor element.

FIG. 3B illustrates one embodiment of a sensing device coupled to aprocessing device.

FIG. 3C illustrates one embodiment of a relaxation oscillator formeasuring capacitance on a sensor element.

FIG. 3D illustrates a schematic of one embodiment of a circuit includinga sigma-delta modulator and a digital filter for measuring capacitanceon a sensor element.

FIG. 4A illustrates a block diagram of one embodiment of an electronicdevice including a processing device that includes a capacitance sensorfor measuring the capacitance on a touch panel in a first mode.

FIG. 4B illustrates one embodiment of the electronic device of FIG. 4Ain a second mode.

FIG. 4C illustrates another embodiment of the electronic device of FIG.4A in a second mode.

FIG. 5 illustrates a block diagram of one embodiment of an electronicdevice including a processing device that includes capacitance sensorsfor measuring the capacitance on a slider.

FIG. 6 illustrates a block diagram of one embodiment of an electronicdevice including a processing device that includes two capacitancesensors for measuring the capacitance on a sensor array.

FIG. 7A illustrates a back-side view of one embodiment of a touch panelhaving two touch-sensor buttons and a ground conductor surrounding thetwo touch-sensor buttons.

FIG. 7B illustrates a back-side view of one embodiment of a touch panelhaving three touch-sensor buttons and three ground conductors eachsurrounding one of the three touch-sensor buttons.

FIG. 7C illustrates a front-side view of one embodiment of a touch panelhaving four touch-sensor buttons in a first zone and four touch-sensorbuttons in a second zone, and a ground conductor surrounding the eighttouch-sensor buttons.

FIG. 8 illustrates a graph of a sensitivity of a single touch-sensorbutton.

FIG. 9 illustrates a top-side view and a bottom-side view of oneembodiment of a case of a mobile handset having two touch-sensor buttonsand a ground conductor for button-activation sensing and proximitysensing.

FIG. 10 illustrates one embodiment of a selection circuit coupled to ananalog bus for measuring capacitance on the sensor elements and theground conductor.

FIG. 11 illustrates a flow chart of one embodiment of a method forbutton-activation sensing and proximity sensing.

FIG. 12 illustrates a flow chart of one embodiment of a method forcoupling a group of sensor elements together when in a reduced powermode.

DETAILED DESCRIPTION

Described herein are apparatuses and methods for integrated proximityand button-activation sensing using already existing hardware of thecapacitance sensing device. The following description sets forthnumerous specific details such as examples of specific systems,components, methods, and so forth, in order to provide a goodunderstanding of several embodiments of the present invention. It willbe apparent to one skilled in the art, however, that at least someembodiments of the present invention may be practiced without thesespecific details. In other instances, well-known components or methodsare not described in detail or are presented in simple block diagramformat in order to avoid unnecessarily obscuring the present invention.Thus, the specific details set forth are merely exemplary. Particularimplementations may vary from these exemplary details and still becontemplated to be within the spirit and scope of the present invention.

Embodiments of a method and apparatus are described to couple a group ofsensor elements together in one mode to collectively measure acapacitance on the group of sensor elements, in addition to individuallymeasuring a capacitance on each of the sensor elements in another mode.The embodiments described herein use the sensor elements of thetouch-sensor buttons to perform both proximity sensing andbutton-activation sensing. In one embodiment, the touch-sensor buttonsare used individually for button-activation sensing, and thetouch-sensor buttons are used collectively for proximity detection. Inanother embodiment, the touch-sensor buttons are used individually forbutton-activation sensing, and the touch-sensor buttons and a groundconductor that surrounds the touch-sensor buttons are collectively usedfor proximity detection. In another embodiment, any conductive material(e.g., metal) of a housing of an electronic device is used for proximitydetection. As such, the embodiments described herein do not use anadditional proximity sensor (e.g., dedicated, discrete proximity sensor)to detect a presence of a conductive object in proximity to a device,but use the already existing conductive elements (e.g., sensor elements,ground conductors, or other conductive material present in theelectronic device) to detect both button-activations as well asproximity activations (e.g., proximity events, such as activating adisplay).

In one embodiment of the method, a presence of a conductive object on adevice (e.g., button-activation sensing) is detected by individuallymeasuring a capacitance on each sensor element of the device, and apresence of the conductive object in proximity to the device (e.g.,proximity event) is detected by collectively measuring a capacitance ona group of couple sensor elements. In one embodiment, the sensitivity ofthe touch-sensor button can be configured so that the touch-sensorbutton is activated when the conductive object is on the touch-sensorbutton, such as touching an area of the overlay that corresponds to thetouch-sensor device. As described above, sensitivity of the sensorelement can be tuned to responds when the user actually touches (e.g.,with the conductive object) the surface of the overlay. The sensorelements as described herein are individually configured to be tuned torespond when the user actually touches the overlay to register abutton-activation (e.g., capacitive button sensor). The sensor elementsare also configured to be tuned to response before the user touches theoverlay to register a proximity event when coupled together (e.g.,proximity sensor).

In one embodiment, the apparatus includes a processing device, andmultiple sensor elements coupled to the processing device. Theprocessing device may be individually coupled to the processing devicein a first mode to detect a presence of a conductive object on thedevice, and a group of sensor elements are collectively coupled to theprocessing device in a second mode to detect a presence of a conductiveobject in proximity to the device.

Touch-sensitive devices operate on a scanning basis. Each sensor elementis connected to the capacitance sensing circuit in turn through anelectronic switch, and its capacitance is measured in a first mode. In asecond mode, rather than measuring the capacitance of each of the sensorelements in turn, a group of the sensor elements are connected together,and a single “coarse” measurement of the total aggregate capacitance onthe group of sensor elements is made. If the total aggregate capacitanceis greater than a pre-determined minimum value (e.g., a low-passfiltered version of recent capacitance measurements), then a proximityevent has been determined, and a corresponding proximity operation maybe performed, such as lighting a backlight on a display, as well asother user input functions.

In one embodiment, the group of sensor elements can be all of the sensorelements in the touch-sensitive device. Alternatively, less than all ofthe sensor elements, for example, ½, ⅓, ¼, or other fractions of thesensor elements can be coupled together in alternating ornon-alternating patterns. In one exemplary embodiment, when implementinga slider, which includes a number of closely-located sensor elements,half of the sensor elements may be coupled together for collectivelymeasuring the capacitance on the slider (e.g., “coarse” measurement) inthe second mode, while all of the sensor elements are individuallymeasured in the first mode. This may have the advantage of reducing thebackground “parasitic” capacitance to ground, and thus, reducing thetime taken to make the “coarse” measurement in the second mode sinceless than all of the sensor elements are coupled together in the secondmode. Similarly, in one embodiment of a touchpad implementation, onlythe rows or columns, but not both may be connected together when takingthe “coarse” measurement on the coupled sensor elements during thesecond mode. In another embodiment, only half of the rows or columns(e.g., alternating rows or columns) are coupled together to make the“coarse” measurement during the second mode. In another embodiment, afirst group of sensor elements are coupled together in a first zone, anda second group of sensor elements are coupled together in a second zone.A first capacitance measurement is made on the sensor elements of thefirst zone, and second capacitance measurement is made on the sensorelements of the second zone. A first proximity event is determined ifthe conductive object is detected in proximity to the first zone usingthe first capacitance measurement, and a second proximity event isdetermined if the conductive object is detected in proximity to thesecond zone using the second capacitance measurement. A buttonactivation is determined when the conductive object is detected on(e.g., touching the area of the overlay that corresponds to) one of thesensor elements. Determination of the first and second proximity eventsmay trigger separate operations, such as activating respective portionsof a display, or the like. Determination of the button activation maytrigger a button operation, such as input entry, or the like.Alternatively, other configurations are possible.

By making only a single capacitance measurement during each sensinginterval when detecting the presence of the conductive object inproximity to the device, the time taken to determine whether aconductive object has recently become present is greatly reduced. Thus,the power consumption in the proximity sensing mode is similarlyreduced, such as by reducing the amount of current consumed to determineif a conductive object is in proximity to the device. The proximitysensing may be used in a “sleep” mode that is a reduced power mode, ascompared to the active or normal mode. The parasitic capacitance of thesensor elements to ground may be greater when all of the sensor elementsare connected together than for an individual sensor element, and thetime taken to measure the capacitance may be proportional to thecapacitance to ground. For example, in a 40-button remote controlexample, the time taken to measure the capacitance of all 40 buttonsconnected together may be 500 μs, as opposed to the 250 μs for anindividual button. As such, when detecting the presence of theconductive object in proximity to the device (e.g., in the sleep mode),the “sleep” current may be reduced from 250 μA to 12.5 μA. Upondetermining that the conductive object is in proximity to the device,the device may transition to an active or normal state, in which thedevice is configured to individually measure the capacitance on each ofthe sensor elements to detect the presence of the conductive object on(e.g., touching a surface of the overlay correspond to) one of thesensor elements of the device. The embodiments described herein mayprovide an advantage of using capacitance sensing in remote control andother battery-operated devices because the power consumption in thereduced power mode is reduced.

As the combined area of all or a fraction of the sensor elements is muchgreater than that of a single sensor element, the capacitance betweenthe combined area and a finger that is close, but not touching thesensor elements is much greater than between the finger and a singlesensor element. This characteristic may be used to provide additionalfeatures, such as, for example, a remote control could potentiallydetect a hand moved over it at several inches distance. This could beused to turn on a backlight, enabling a user to locate the remotecontrol in a dark room simply by waving a hand over the approximatelocation of the remote control, for example, on a side table. Similarly,the embodiments described herein may be used to detect and interpretgestures made in the air over the touch-sensitive device (e.g.,touchpad); such gestures could be separate from and independent of theusual gestures typically recognized by the touch-sensitive device. Forexample, in one embodiment, the page-up and page-down gestures areactivated by waving a finger or hand over the top of the touch-sensitivedevice (e.g., touchpad) without touching the surface. Alternatively,other types of gestures may be implemented.

It should be noted that in other embodiments, the capacitance sensingapplications may use a pair of capacitance sensing circuits, allowingtwo buttons (or sensor elements of a touchpad or a slider) to be sensedsimultaneously. In one embodiment, half of the sensor elements active inone mode may be connected to each of the sensing circuits, and two“coarse” capacitance measurements are made simultaneously. This may havethe advantage of reducing the time taken to make the capacitancemeasurement, as the parasitic capacitance of each group is less than theparasitic capacitance when both groups are combined.

The embodiments described herein may provide an advantage overconventional capacitance sensing systems by allowing bothbutton-activation sensing and proximity sensing without using anadditional proximity sensor. The embodiments described herein may alsoprovide an advantage over conventional capacitance sensing systems byreducing sleep current to a level where capacitance sensing becomes aviable option in applications where the current consumption ofconventional capacitance sensing systems is unacceptably high. Theembodiments described herein may also provide the benefit of increasingbattery life of the device. The embodiments described herein may alsoenable detection of conductive objects (e.g., fingers or hands) atgreater distances than conventional systems.

It should be noted that the embodiments described herein are differentthan sensing devices that use a 2-stage sensing process. In the 2-stagesensing process, the sensor elements are divided into multiple groups,and each group of sensor elements is connected together and theaggregate capacitance of each group is measured to determine in whichgroup the finger is detected. Then when it has been determined in whichgroup the finger is located, each of the sensor elements of that groupis sensed individually. In the embodiments described herein, only asingle group of sensor elements (e.g., a fraction or all of the sensorelements) is measured, rather than multiple groups of sensor elementsthat are measured each in turn. The embodiments described herein alsoonly measure a group of coupled sensor elements when detecting apresence of a conductive object in proximity to the device.

FIG. 2 illustrates a block diagram of one embodiment of an electronicsystem having a processing device for detecting a presence of aconductive object. Electronic system 200 includes processing device 210,touch-sensor pad 220, touch-sensor slider 230, touch-sensor buttons 240,host processor 250, embedded controller 260, and non-capacitance sensorelements 270. The processing device 210 may include analog and/ordigital general purpose input/output (“GPIO”) ports 207. GPIO ports 207may be programmable. GPIO ports 207 may be coupled to a ProgrammableInterconnect and Logic (“PIL”), which acts as an interconnect betweenGPIO ports 207 and a digital block array of the processing device 210(not illustrated). The digital block array may be configured toimplement a variety of digital logic circuits (e.g., DAC, digitalfilters, digital control systems) using, in one embodiment, configurableuser modules (“UMs”). The digital block array may be coupled to a systembus (not illustrated). Processing device 210 may also include memory,such as random access memory (RAM) 205 and program flash 204. RAM 205may be static RAM (SRAM) or the like, and program flash 204 may be anon-volatile storage, or the like, which may be used to store firmware(e.g., control algorithms executable by processing core 202 to implementoperations described herein). Processing device 210 may also include amemory controller unit (MCU) 203 coupled to memory and the processingcore 202.

The processing device 210 may also include an analog block array (notillustrated). The analog block array is also coupled to the system bus.Analog block array also may be configured to implement a variety ofanalog circuits (e.g., ADC, analog filters) using, in one embodiment,configurable UMs. The analog block array may also be coupled to the GPIO207.

As illustrated, capacitance sensor 201 may be integrated into processingdevice 210. Capacitance sensor 201 may include analog I/O for couplingto an external component, such as touch-sensor pad 220, touch-sensorslider 230, touch-sensor buttons 240, and/or other devices. Capacitancesensor 201 and processing device 210 are described in more detail below.

It should be noted that the embodiments described herein are not limitedto touch-sensor pads for notebook implementations, but can be used inother capacitive sensing implementations, for example, the sensingdevice may be a touch screen, a touch-sensor slider 230, or atouch-sensor button 240 (e.g., capacitance sensing button). It shouldalso be noted that the embodiments described herein may be implementedin other sensing technologies than capacitive sensing, such asresistive, optical imaging, surface acoustical wave (SAW), infrared,dispersive signal, and strain gauge technologies. Similarly, theoperations described herein are not limited to notebook pointeroperations, but can include other operations, such as lighting control(dimmer), temperature or environmental control, volume control, graphicequalizer control, speed control, or other control operations requiringgradual or discrete adjustments. It should also be noted that theseembodiments of capacitive sensing implementations may be used inconjunction with non-capacitive sensing elements, including but notlimited to pick buttons, sliders (ex. display brightness and contrast),scroll-wheels, multi-media control (ex. volume, track advance, etc.)handwriting recognition and numeric keypad operation.

In one embodiment, the electronic system 200 includes a touch-sensor pad220 coupled to the processing device 210 via bus 221. Touch-sensor pad220 may include a two-dimension sensor array. The two-dimension sensorarray includes multiple sensor elements, organized as rows and columns.In another embodiment, the electronic system 200 includes a touch-sensorslider 230 coupled to the processing device 210 via bus 231.Touch-sensor slider 230 may include a single-dimension sensor array. Thesingle-dimension sensor array includes multiple sensor elements,organized as rows, or alternatively, as columns. In another embodiment,the electronic system 200 includes touch-sensor buttons 240 coupled tothe processing device 210 via bus 241. Touch-sensor button 240 mayinclude a single-dimension or multi-dimension sensor array. The single-or multi-dimension sensor array includes multiple sensor elements. For atouch-sensor button, the sensor elements may be coupled together todetect a presence of a conductive object over the entire surface of thesensing device. Alternatively, the touch-sensor button 240 has a singlesensor element to detect the presence of the conductive object. In oneembodiment, the touch-sensor button 240 may be a capacitance sensorelement. Capacitance sensor elements may be used as non-contact sensors.These sensor elements, when protected by an insulating layer, offerresistance to severe environments.

The electronic system 200 may include any combination of one or more ofthe touch-sensor pad 220, touch-sensor slider 230, and/or touch-sensorbutton 240. In another embodiment, the electronic system 200 may alsoinclude non-capacitance sensor elements 270 coupled to the processingdevice 210 via bus 271. The non-capacitance sensor elements 270 mayinclude buttons, light emitting diodes (LEDs), and other user interfacedevices, such as a mouse, a keyboard, a display, or other functionalkeys that do not require capacitance sensing. In one embodiment, buses271, 241, 231, and 221 may be a single bus. Alternatively, these busesmay be configured into any combination of one or more separate buses.

The processing device 210 may also provide value-added functionalitysuch as keyboard control integration, LEDs, battery charger, and generalpurpose I/O, as illustrated as non-capacitance sensor elements 270.Non-capacitance sensor elements 270 are coupled to the GPIO 207.

Processing device 210 may include internal oscillator/clocks 206 andcommunication block 208. The oscillator/clocks block 206 provides clocksignals to one or more of the components of processing device 210.Communication block 208 may be used to communicate with an externalcomponent, such as a host processor 250, via host interface (I/F) 251.Alternatively, processing block 210 may also be coupled to embeddedcontroller 260 to communicate with the external components, such as host250. Interfacing to the host 250 can be through various methods. In oneexemplary embodiment, interfacing with the host 250 may be done using astandard PS/2 interface to connect to an embedded controller 260, whichin turn sends data to the host 250 via a low pin count (LPC) interface.In some instances, it may be beneficial for the processing device 210 todo both touch-sensor pad and keyboard control operations, therebyfreeing up the embedded controller 260 for other housekeeping functions.In another exemplary embodiment, interfacing may be done using auniversal serial bus (USB) interface directly coupled to the host 250via host interface 251. Alternatively, the processing device 210 maycommunicate to external components, such as the host 250 using industrystandard interfaces, such as USB, PS/2, inter-integrated circuit (I2C)bus, system packet interfaces (SPI), or the like. The host 250 and/orembedded controller 260 may be coupled to the processing device 210 witha ribbon or flex cable from an assembly, which houses the sensing deviceand processing device.

In one embodiment, the processing device 210 is configured tocommunicate with the embedded controller 260 or the host 250 to sendand/or receive data. The data may be a command or alternatively asignal. In an exemplary embodiment, the electronic system 200 mayoperate in both standard-mouse compatible and enhanced modes. Thestandard-mouse compatible mode utilizes the HID class drivers alreadybuilt into the Operating System (OS) software of host 250. These driversenable the processing device 210 and sensing device to operate as astandard pointer control user interface device, such as a two-buttonPS/2 mouse. The enhanced mode may enable additional features such asscrolling or disabling the sensing device, such as when a mouse isplugged into the notebook. Alternatively, the processing device 210 maybe configured to communicate with the embedded controller 260 or thehost 250, using non-OS drivers, such as dedicated touch-sensor paddrivers, or other drivers known by those of ordinary skill in the art.

In one embodiment, the processing device 210 may operate to communicatedata (e.g., commands or signals) using hardware, software, and/orfirmware, and the data may be communicated directly to the processingdevice of the host 250, such as a host processor, or alternatively, maybe communicated to the host 250 via drivers of the host 250, such as OSdrivers, or other non-OS drivers. It should also be noted that the host250 may directly communicate with the processing device 210 via hostinterface 251.

In one embodiment, the data sent to the host 250 from the processingdevice 210 includes click, double-click, movement of the pointer,scroll-up, scroll-down, scroll-left, scroll-right, step Back, and stepForward. In another embodiment, the data sent to the host 250 includesthe position or location of the conductive object on the sensing device.Alternatively, other user interface device commands may be communicatedto the host 250 from the processing device 210. These commands may bebased on gestures occurring on the sensing device that are recognized bythe processing device, such as tap, push, hop, drag, and zigzaggestures. Alternatively, other commands may be recognized. Similarly,signals may be sent that indicate the recognition of these operations.

In particular, a tap gesture, for example, may be when the finger (e.g.,conductive object) is on the sensing device for less than a thresholdtime. If the time the finger is placed on the touchpad is greater thanthe threshold time it may be considered to be a movement of the pointer,in the x- or y-axes. Scroll-up, scroll-down, scroll-left, andscroll-right, step back, and step-forward may be detected when theabsolute position of the conductive object is within a pre-defined area,and movement of the conductive object is detected.

Processing device 210 may reside on a common carrier substrate such as,for example, an integrated circuit (IC) die substrate, a multi-chipmodule substrate, or the like. Alternatively, the components ofprocessing device 210 may be one or more separate integrated circuitsand/or discrete components. In one exemplary embodiment, processingdevice 210 may be a Programmable System on a Chip (PSoC®) processingdevice, developed by Cypress Semiconductor Corporation, San Jose, Calif.Alternatively, processing device 210 may be one or more other processingdevices known by those of ordinary skill in the art, such as amicroprocessor or central processing unit, a controller, special-purposeprocessor, digital signal processor (DSP), an application specificintegrated circuit (ASIC), a field programmable gate array (FPGA), orthe like. In an alternative embodiment, for example, the processingdevice may be a network processor having multiple processors including acore unit and multiple microengines. Additionally, the processing devicemay include any combination of general-purpose processing device(s) andspecial-purpose processing device(s).

It should also be noted that the embodiments described herein are notlimited to having a configuration of a processing device coupled to ahost, but may include a system that measures the capacitance on thesensing device and sends the raw data to a host computer where it isanalyzed by an application. In effect the processing that is done byprocessing device 210 may also be done in the host. In anotherembodiment, the processing device 210 is the host.

In one embodiment, the method and apparatus described herein may beimplemented in a fully self-contained touch-sensor pad, which outputsfully processed x/y movement and gesture data signals or data commandsto a host. In another embodiment, the method and apparatus may beimplemented in a touch-sensor pad, which outputs x/y movement data andalso finger presence data to a host, and where the host processes thereceived data to detect gestures. In another embodiment, the method andapparatus may be implemented in a touch-sensor pad, which outputs rawcapacitance data to a host, where the host processes the capacitancedata to compensate for quiescent and stray capacitance, and calculatesx/y movement and detects gestures by processing the capacitance data.Alternatively, the method and apparatus may be implemented in atouch-sensor pad, which outputs pre-processed capacitance data to ahost, where the touchpad processes the capacitance data to compensatefor quiescent and stray capacitance, and the host calculates x/ymovement and detects gestures from the pre-processed capacitance data.Alternatively, other configurations are possible.

In one embodiment, the electronic system that includes the embodimentsdescribed herein may be implemented in a conventional laptoptouch-sensor pad. Alternatively, it may be implemented in a wired orwireless keyboard integrating a touch-sensor pad, which is itselfconnected to a host. In such an implementation, the processing describedabove as being performed by the “host” may be performed in part or inwhole by the keyboard controller, which may then pass fully processed,pre-processed or unprocessed data to the system host. In anotherembodiment, the embodiments may be implemented in a mobile handset(e.g., cellular or mobile phone) or other electronic devices where thetouch-sensor pad may operate in one of two or more modes. For example,the touch-sensor pad may operate either as a touch-sensor pad for x/ypositioning and gesture recognition, or as a keypad or other arrays oftouch-sensor buttons and/or sliders. Alternatively, the touch-sensorpad, although configured to operate in the two modes, may be configuredto be used only as a keypad.

Capacitance sensor 201 may be integrated into the processing device 210,or alternatively, in a separate IC. Alternatively, descriptions ofcapacitance sensor 201 may be generated and compiled for incorporationinto other integrated circuits. For example, behavioral level codedescribing capacitance sensor 201, or portions thereof, may be generatedusing a hardware description language, such as VHDL or Verilog, andstored to a machine-accessible medium (e.g., Flash ROM, CD-ROM, harddisk, floppy disk, etc.). Furthermore, the behavioral level code can becompiled into register transfer level (“RTL”) code, a netlist, or even acircuit layout and stored to a machine-accessible medium. The behaviorallevel code, the RTL code, the netlist, and the circuit layout allrepresent various levels of abstraction to describe capacitance sensor201.

It should be noted that the components of electronic system 200 mayinclude all the components described above. Alternatively, electronicsystem 200 may include only some of the components described above, orinclude additional components not listed herein.

In one embodiment, electronic system 200 may be used in a notebookcomputer. Alternatively, the electronic device may be used in otherapplications, such as a mobile handset, a personal data assistant (PDA),a kiosk, a keyboard, a television, a remote control, a monitor, ahandheld multi-media device, a handheld video player, a handheld gamingdevice, or a control panel.

In one embodiment, capacitance sensor 201 may be a capacitance sensingrelaxation oscillator (CSR). The CSR may be coupled to an array ofsensor elements using a current-programmable relaxation oscillator, ananalog multiplexer, digital counting functions, and high-level softwareroutines to compensate for environmental and physical sensor elementvariations. The sensor array may include combinations of independentsensor elements, sliding sensor elements (e.g., touch-sensor slider),and touch-sensor sensor element pads (e.g., touch pad or touch screen)implemented as a pair of orthogonal sliding sensor elements. The CSR mayinclude physical, electrical, and software components. The physicalcomponents may include the physical sensor element itself, typically apattern constructed on a printed circuit board (PCB) with an insulatingcover, a flexible membrane, or a transparent overlay. The electricalcomponent may include an oscillator or other means to convert acapacitance into a measured value. The electrical component may alsoinclude a counter or timer to measure the oscillator output. Thesoftware component may include detection and compensation algorithms toconvert the count value into a sensor element detection decision (alsoreferred to as switch detection decision). For example, in the case ofslider sensor elements or X-Y touch-sensor sensor element pads, acalculation for finding position of the conductive object to greaterresolution than the physical pitch of the sensor elements may be used.

It should be noted that there are various known methods for measuringcapacitance. Although some embodiments described herein are describedusing a relaxation oscillator, the present embodiments are not limitedto using relaxation oscillators, but may include other methods, such ascurrent versus voltage phase shift measurement, resistor-capacitorcharge timing, capacitive bridge divider, charge transfer, sigma-deltamodulators, charge-accumulation circuits, or the like.

The current versus voltage phase shift measurement may include drivingthe capacitance through a fixed-value resistor to yield voltage andcurrent waveforms that are out of phase by a predictable amount. Thedrive frequency can be adjusted to keep the phase measurement in areadily measured range. The resistor-capacitor charge timing may includecharging the capacitor through a fixed resistor and measuring timing onthe voltage ramp. Small capacitance values may require very largeresistors for reasonable timing. The capacitive bridge divider mayinclude driving the capacitor under test through a fixed referencecapacitor. The reference capacitor and the capacitor under test form avoltage divider. The voltage signal may be recovered with a synchronousdemodulator, which may be done in the processing device 210. The chargetransfer may be conceptually similar to an R-C charging circuit. In thismethod, C_(P) is the capacitance being sensed. C_(SUM) is the summingcapacitor, into which charge is transferred on successive cycles. At thestart of the measurement cycle, the voltage on C_(SUM) is discharged.The voltage on C_(SUM) increases exponentially (and only slightly) witheach clock cycle. The time for this voltage to reach a specificthreshold is measured with a counter. Additional details regarding thesealternative embodiments have not been included so as to not obscure thepresent embodiments, and because these alternative embodiments formeasuring capacitance are known by those of ordinary skill in the art.

FIG. 3A illustrates a varying capacitance sensor element. In its basicform, a capacitance sensor element 300 is a pair of adjacent conductors301 and 302. There is a small edge-to-edge capacitance, but the intentof sensor element layout is to minimize the parasitic capacitance C_(P)between these conductors. When a conductive object 303 (e.g., finger) isplaced in proximity to the two conductors 301 and 302, there is acapacitance between electrode 301 and the conductive object 303 and asimilar capacitance between the conductive object 303 and the otherelectrode 302. The capacitance between the electrodes when no conductiveobject 303 is present is the base capacitance C_(p) that may be storedas a baseline value. There is also a total capacitance (C_(P)+C_(F)) onthe sensor element 300 when the conductive object 303 is present on orin close proximity to the sensor element 300. The baseline capacitancevalue C_(P) may be subtracted from the total capacitance when theconductive object 303 is present to determine the change in capacitance(e.g., capacitance variation C_(F)) when the conductive object 303 ispresent and when the conductive object 303 is not present on the sensorelement. Effectively, the capacitance variation C_(F) can be measured todetermine whether a conductive object 303 is present or not (e.g.,sensor activation) on the sensor element 300.

Capacitance sensor element 300 may be used in a capacitance sensorarray. The capacitance sensor array is a set of capacitors where oneside of each capacitor is connected to a system ground. When thecapacitance sensor element 300 is used in the sensor array, when theconductor 301 is sensed, the conductor 302 is connected to ground, andwhen the conductor 302 is sensed, the conductor 301 is connected toground. Alternatively, when the sensor element is used for atouch-sensor button, the sensor element is sensed and the sensed buttonarea may be surrounded by a fixed ground. The presence of the conductiveobject 303 increases the capacitance (C_(P)+C_(F)) of the sensor element300 to ground. Determining sensor element activation is then a matter ofmeasuring change in the capacitance (C_(F)) or capacitance variation.Sensor element 300 is also known as a grounded variable capacitor.

The conductive object 303 in this embodiment has been illustrated as afinger. Alternatively, this technique may be applied to any conductiveobject, for example, a conductive door switch, position sensor, orconductive pen in a stylus tracking system (e.g., stylus).

The capacitance sensor element 300 is known as a projected capacitancesensor. Alternatively, the capacitance sensor element 300 may be asurface capacitance sensor that does not make use of rows or columns,but instead makes use of a single linearized field, such as the surfacecapacitance sensor described in U.S. Pat. No. 4,293,734. The surfacecapacitance sensor may be used in touch screen applications.

FIG. 3B illustrates one embodiment of a capacitance sensor element 307coupled to a processing device 210. Capacitance sensor element 307illustrates the capacitance as seen by the processing device 210 on thecapacitance sensing pin 306. As described above, when a conductiveobject 303 (e.g., finger) is placed in proximity to one of theconductors 305, there is a capacitance, C_(F), between the one of theconductors 305 and the conductive object 303 with respect to ground.This ground, however, may be a floating ground. Also, there is acapacitance, C_(P), between the conductors 305, with one of theconductors 305 being connected to a system ground. The groundedconductor may be coupled to the processing device 210 using GPIO pin308. The conductors 305 may be metal, or alternatively, the conductorsmay be conductive ink (e.g., carbon ink), conductive ceramic (e.g.,transparent conductors of indium tin oxide (ITO)), conductive polymers,or the like. In one embodiment, the grounded conductor may be anadjacent sensor element. Alternatively, the grounded conductor may beother grounding mechanisms, such as a surrounding ground plane.Accordingly, the processing device 210 can measure the change incapacitance, capacitance variation C_(F), as the conductive object is inproximity to one of the conductors 305. Above and below the conductorthat is closest to the conductive object 303 is dielectric material 304.The dielectric material 304 above the conductor 305 can be an overlay.The overlay may be non-conductive material used to protect the circuitryfrom environmental conditions and electrostatic discharge (ESD), and toinsulate the user's finger (e.g., conductive object) from the circuitry.Capacitance sensor element 307 may be a sensor element of a touch-sensorpad, a touch-sensor slider, or a touch-sensor button.

FIG. 3C illustrates one embodiment of a relaxation oscillator. Therelaxation oscillator 350 is formed by the capacitance to be measured oncapacitor 351, a charging current source 352, a comparator 353, and areset switch 354 (also referred to as a discharge switch). It should benoted that capacitor 351 is representative of the capacitance measuredon a sensor element of a sensor array. The relaxation oscillator iscoupled to drive a charging current (Ic) 357 in a single direction ontoa device under test (“DUT”) capacitor, capacitor 351. As the chargingcurrent piles charge onto the capacitor 351, the voltage across thecapacitor increases with time as a function of Ic 357 and itscapacitance C. Equation (1) describes the relation between current,capacitance, voltage, and time for a charging capacitor.CdV=I _(C) dt  (1)

The relaxation oscillator begins by charging the capacitor 351, at afixed current Ic 357, from a ground potential or zero voltage until thevoltage across the capacitor 351 at node 355 reaches a reference voltageor threshold voltage, V_(TH) 360. At the threshold voltage V_(TH) 360,the relaxation oscillator allows the accumulated charge at node 355 todischarge (e.g., the capacitor 351 to “relax” back to the groundpotential) and then the process repeats itself. In particular, theoutput of comparator 353 asserts a clock signal F_(OUT) 356 (e.g.,F_(OUT) 356 goes high), which enables the reset switch 354. Thisdischarges the capacitor at node 355 to ground and the charge cyclestarts again. The relaxation oscillator outputs a relaxation oscillatorclock signal (F_(OUT) 356) having a frequency (f_(RO)) dependent uponcapacitance C of the capacitor 351 and charging current Ic 357.

The comparator trip time of the comparator 353 and reset switch 354 adda fixed delay. The output of the comparator 353 is synchronized with areference system clock to guarantee that the reset time is long enoughto completely discharge capacitor 351. This sets a practical upper limitto the operating frequency. For example, if capacitance C of thecapacitor 351 changes, then f_(RO) changes proportionally according toEquation (1). By comparing f_(RO) of F_(OUT) 356 against the frequency(f_(REF)) of a known reference system clock signal (REF CLK), the changein capacitance ΔC can be measured. Accordingly, equations (2) and (3)below describe that a change in frequency between F_(OUT) 356 and REFCLK is proportional to a change in capacitance of the capacitor 351.ΔC∝Δf, where  (2)Δf=f _(RO) −f _(REF).  (3)

In one embodiment, a frequency comparator may be coupled to receiverelaxation oscillator clock signal (F_(OUT) 356) and REF CLK, comparetheir frequencies f_(RO) and f_(REF), respectively, and output a signalindicative of the difference Δf between these frequencies. By monitoringΔf one can determine whether the capacitance of the capacitor 351 haschanged.

In one exemplary embodiment, the relaxation oscillator 350 may be builtusing a programmable timer (e.g., 555 timer) to implement the comparator353 and reset switch 354. Alternatively, the relaxation oscillator 350may be built using other circuitry. Relaxation oscillators are known bythose of ordinary skill in the art, and accordingly, additional detailsregarding their operation have not been included so as to not obscurethe present embodiments. The capacitor charging current for therelaxation oscillator 350 may be generated in a register programmablecurrent output DAC (also known as IDAC). Accordingly, the current source352 may be a current DAC or IDAC. The IDAC output current may be set byan 8-bit value provided by the processing device 210, such as from theprocessing core 202. The 8-bit value may be stored in a register, inmemory, or the like.

In many capacitance sensor element designs, the two “conductors” (e.g.,301 and 302) of the sensing capacitor are actually adjacent sensorelements that are electrically isolated (e.g., PCB pads or traces), asindicated in FIG. 3A. Typically, one of these conductors is connected toa system ground. Layouts for touch-sensor slider (e.g., linear slidesensor elements) and touch-sensor pad applications have sensor elementsthat may be immediately adjacent. In these cases, all of the sensorelements that are not active are connected to a system ground throughthe GPIO 207 of the processing device 210 dedicated to that pin. Theactual capacitance between adjacent conductors is small (C_(P)), but thecapacitance of the active conductor (and its PCB trace back to theprocessing device 210) to ground, when detecting the presence of theconductive object 303, may be considerably higher (C_(P)+C_(F)). Thecapacitance of two parallel conductors is given by the followingequation:

$\begin{matrix}{C = {{ɛ_{0} \cdot ɛ_{R} \cdot \frac{A}{d}} = {{ɛ_{R} \cdot 8.85 \cdot \frac{A}{d}}{{pF}/m}}}} & (4)\end{matrix}$

The dimensions of equation (4) are in meters. This is a very simplemodel of the capacitance. The reality is that there are fringing effectsthat substantially increase the sensor element-to-ground (and PCBtrace-to-ground) capacitance.

There is some variation of sensor element sensitivity as a result ofenvironmental factors. A baseline update routine, which compensates forthis variation, may be provided in the high-level APIs.

As described above with respect to the relaxation oscillator 350, when afinger or conductive object is placed on the sensor element, thecapacitance increases from C_(P) to C_(P)+C_(F) so the relaxationoscillator output signal 356 (F_(OUT)) decreases in frequency. Therelaxation oscillator output signal 356 (F_(OUT)) may be fed to adigital counter for measurement. There are two methods for counting therelaxation oscillator output signal 356: frequency measurement andperiod measurement. Additional details of the relaxation oscillator anddigital counter are known by those of ordinary skill in the art, andaccordingly a detailed description regarding them has not been included.It should also be noted, that the embodiments described herein are notlimited to using relaxation oscillators, but may include other sensingcircuitry for measuring capacitance, such as versus voltage phase shiftmeasurement, resistor-capacitor charge timing, capacitive bridgedivider, charge transfer, sigma-delta modulators, charge-accumulationcircuits, or the like.

FIG. 3D illustrates a schematic of one embodiment of a circuit 375including a sigma-delta modulator 360 and a digital filter 390 formeasuring capacitance on a sensor element 351. Circuit 375 includes aswitching circuit 370, switching clock source 380, sigma-delta modulator360, and digital filter 390 for measuring the capacitance on sensorelement 351. Sensor element 351 may be a sensor element of a sensorarray, and is represented as a switching capacitor C_(X) in themodulator feedback loop. Alternatively, sensor element 351 may be asingle sensor element, such as used in a touch-sensor button. Switchingcircuit 370 includes two switches Sw₁ 371 and Sw₂ 372. The switches Sw₁371 and Sw₂ 372 operate in two, non-overlapping phases (also known asbreak-before-make configuration). These switches together with sensingcapacitor C_(x) 351 form the switching capacitor equivalent resistor,which provides the modulator capacitor C_(mod) 363 of sigma-deltamodulator 360 charge current (as illustrated in FIG. 3D) or dischargecurrent (not illustrated) during one of the two phases.

The sigma-delta modulator 360 includes the comparator 361, latch 362,modulator capacitor C_(mod) 363, modulator feedback resistor 365, whichmay also be referred to as bias resistor 365, and voltage source 366.The output of the comparator may be configured to toggle when thevoltage on the modulator capacitor 363 crosses a reference voltage 364.The reference voltage 364 may be a pre-programmed value, and may beconfigured to be programmable. The sigma-delta modulator 360 alsoincludes a latch 362 coupled to the output of the comparator 361 tolatch the output of the comparator 361 for a given amount of time, andprovide as an output, output 392. The latch may be configured to latchthe output of the comparator based on a clock signal from the gatecircuit 382 (e.g., oscillator signal from the oscillator 381). Inanother embodiment, the sigma-delta modulator 360 includes asynchronized latch that operates to latch an output of the comparatorfor a pre-determined length of time. The output of the comparator may belatched for measuring or sampling the output signal of the comparator361 by the digital filter 390.

Sigma-delta modulator 360 is configured to keep the voltage on themodulator capacitor 363 close to reference voltage V_(ref) 364 byalternatively connecting the switching capacitor resistor (e.g.,switches Sw₁ 371 and Sw₂ 372 and sensing capacitor C_(x) 351) to themodulator capacitor 363. The output 392 of the sigma-delta modulator 360(e.g., output of latch 362) is feedback to the switching clock circuit380, which controls the timing of the switching operations of switchesSw₁ 371 and Sw₂ 372 of switching circuit 370. For example, in thisembodiment, the switching clock circuit 380 includes an oscillator 381and gate 382. Alternatively, the switching clock circuit 380 may includea clock source, such as a spread spectrum clock source (e.g.,pseudo-random signal (PRS)), a frequency divider, a pulse widthmodulator (PWM), or the like. The output 392 of the sigma-deltamodulator 360 is used with an oscillator signal to gate a control signal393, which switches the switches Sw₁ 371 and Sw₂ 372 in anon-overlapping manner (e.g., two, non-overlapping phases). The output392 of the sigma-delta modulator 360 is also output to digital filter390, which filters and/or converts the output into the digital code 391.

In one embodiment of the method of operation, at power on, the modulatorcapacitor 363 has zero voltage and switching capacitor resistor (formedby sensing capacitor Cx 351, and switches Sw₁ 371 and Sw₂ 372) isconnected between Vdd line 366 and modulator capacitor 363. Thisconnection allows the voltage on the modulator capacitor 363 to rise.When this voltage reaches the comparator reference voltage, V_(ref) 364,the comparator 361 toggles and gates the control signal 393 of theswitches Sw₁ 371 and Sw₂ 372, stopping the charge current. Because thecurrent via bias resistors R_(b) 365 continues to flow, the voltage onmodulator capacitor 363 starts dropping. When it drops below thereference voltage 364, the output of the comparator 361 switches again,enabling the modulator capacitor 363 to start charging. The latch 362and the comparator 361 set the sample frequency of the sigma-deltamodulator 360.

The digital filter 390 is coupled to receive the output 392 of thesigma-delta modulator 360. The output 392 of the sigma-delta modulator360 may be a single bit bit-stream, which can be filtered and/orconverted to numerical values using a digital filter 390. In oneembodiment, the digital filter 390 is a counter. In another embodiment,the standard Sinc digital filter can be used. In another embodiment, thedigital filter is a decimator. Alternatively, other digital filters maybe used for filtering and/or converting the output 392 of thesigma-delta modulator 360 to provide the digital code 391. It shouldalso be noted that the output 392 may be output to the decision logic402 or other components of the processing device 210, or to the decisionlogic 451 or other components of the host 250 to process the bitstreamoutput of the sigma-delta modulator 360.

Described below are the mathematical equations that represent theoperations of FIG. 3D. During a normal operation mode, the sigma-deltamodulator 360 keeps these currents equal in the average by keeping thevoltage on the modulator 363 equal to, or close to, the referencevoltage V_(ref) 364. The current of the bias resistor R_(b) 365 is:

$\begin{matrix}{I_{Rb} = \frac{V_{c\;{mod}}}{R_{b}}} & (5)\end{matrix}$The sensing capacitor C_(x) 351 in the switched-capacitor mode hasequivalent resistance:

$\begin{matrix}{R_{c} = \frac{1}{f_{s}C_{x}}} & (6)\end{matrix}$where f_(s) is the operation frequency of the switches (e.g., switchingcircuit 370). If the output 392 of the sigma-delta modulator 360 has aduty cycle of d_(mod), the average current of the switching capacitor351 can be expressed in the following equation (7):

$\begin{matrix}{I_{c} = {d_{mod}\frac{V_{dd} - V_{C\;{mod}}}{R_{c}}}} & (7)\end{matrix}$In the operation mode,

$\begin{matrix}{{I_{Rb} = I_{c}},{V_{C\;{mod}} = {{V_{ref}\mspace{14mu}{{or}:\mspace{14mu}\frac{V_{ref}}{R_{b}}}} = {d_{mod}\frac{V_{dd} - V_{ref}}{R_{c}}}}}} & (8)\end{matrix}$or taking into account that the reference voltage 364 is part of supplyvoltage:

$\begin{matrix}{{V_{ref} = {k_{d}V_{dd}}};{k_{d} = \frac{R_{1}}{R_{1} + R_{2}}}} & (9)\end{matrix}$The Equation (8) can be rewritten in the following form:

$\begin{matrix}{d_{mod} = {{\frac{R_{c}}{R_{b}}\frac{k_{d}}{1 - k_{d}}} = {\frac{1}{f_{s}R_{b}}\frac{k_{d}}{1 - k_{d}}\frac{1}{C_{x}}}}} & (10)\end{matrix}$

The Equation (10) determines the minimum sensing capacitance value,which can be measured with the proposed method at given parameters set:

$\begin{matrix}{{d_{mod} \leq 1},{{{or}:\mspace{14mu} C_{x\;\min}} = {\frac{1}{f_{s}R_{b}}\frac{k_{d}}{1 - k_{d}}}}} & (11)\end{matrix}$

The resolution of this method may be determined by the sigma-deltamodulator duty cycle measurement resolution, which is represented in thefollowing equations:

$\begin{matrix}{{{{\Delta\; d_{mod}} = {\beta\frac{\Delta\; C_{x}}{C_{x}^{2}}}};}{\beta = {\frac{1}{f_{s}R_{b}}\frac{k_{d}}{1 - k_{d}}}}} & (12)\end{matrix}$or after rewriting relatively ΔC_(x), we obtain:

$\begin{matrix}{{\Delta\; C_{x}} = {\frac{1}{\beta}\Delta\; d_{mod}C_{x}^{2}}} & (13)\end{matrix}$

In one exemplary embodiment, the resistance of the bias resistor 365 is20 k ohms (R_(b)=20 k), the operation frequency of the switches is 12MHz (f_(s)=12 MHz), the capacitance on the switching capacitor 351 is 15picofarads (C_(x)=15 pF), and the ratio between Vdd 366 and the voltagereference 364 is 0.25 (k_(d)=0.25), the duty cycle has a 12-bitresolution and the capacitance resolution is 0.036 pF.

In some embodiments of capacitive sensing applications, it may beimportant to get fast data measurements. For example, the modulator canoperate at sample frequency 10 MHz (period is 0.1 microseconds (μs)),for the 12-bit resolution sample, and digital filter as single-typeintegrator/counter the measurement time is approximately 410 μs (e.g.,2¹²*0.1 μs=410 μs). For faster measurement speeds at same resolutions,other types of digital filters may be used, for example, by using theSinc 2 filter, the scanning time at the same resolution may be reducedapproximately 4 times. To do this the sensing method should havesuitable measurement speed. In one embodiment, a good measurement ratemay be accomplished by using a double integrator as the digital filter390.

FIG. 4A illustrates a block diagram of one embodiment of an electronicdevice 400 including a processing device 210 that includes a capacitancesensor 201 for measuring the capacitance on a touch panel 410 in a firstmode 430. The electronic device 400 includes the touch panel 410, whichincludes multiple touch-sensor buttons (e.g., similar to touch-sensorbuttons 240 of FIG. 2), processing device 210, and host 250. Touch panel410 includes sensor elements 355(1)-355(N), where N is a positiveinteger value that represents the number of touch-sensor buttons of thetouch panel 410. Each sensor element 355 corresponds to a button of thetouch panel 410. Although the buttons are described as being part of atouch panel, alternatively, the buttons may be separated in multipletouch panels or the buttons may be individually mounted on the devicewithout the use of a touch panel.

The sensor elements 355(1)-355(N) of touch panel 410 are coupled tomultiple pins of the processing device 210 via an analog bus 401. Eachof the sensor elements 355 are coupled to a pin on the processing device210. The analog bus 401 is coupled to a selection circuit 420. Theselection circuit 420 may be configured to couple the sensor elements355 individually to the capacitance sensor 201 during the first mode 430(illustrated in FIG. 4A), and configured to collectively couple a groupof sensor elements to the capacitance sensor 201 during the second mode440 (illustrated in FIG. 4B), or configured to collectively couple agroup of sensor elements and a ground conductor to the capacitancesensor 201 during the second mode 450 (illustrated in FIG. 4C). Forexample in the first mode 430, as illustrated in FIG. 4A, the firstsensor element 355(1) is selected (as indicated by the black sensorelement of the touch panel 410), and coupled to the capacitance sensor201 to measure the capacitance on the first sensor element 355(1). Afterthe capacitance has been measured on the first sensor element, theselection circuit 420 opens the switch that connects the first sensorelement 355(1) to the capacitance sensor 201, and closes another switchthat connects the capacitance sensor 201 to a subsequent sensor element.This is repeated to individually measure the capacitance on each of thesensor elements 355 during the first mode 430. The processing device 210is configured to perform a capacitance measurement on each of the sensorelements 355(1)-355(N) during each sensing interval when in the firstmode 430.

In one embodiment, the selection circuit 420 is configured tosequentially select the individual sensor elements. In anotherembodiment, the selection circuit 420 is configured to sequentiallyselect sets of sensor elements, such as rows or columns, as describedbelow. The selection circuit 420 may be configured to provide chargecurrent or voltage to the selected sensor elements and to measure acapacitance on the selected sensor elements. In one exemplaryembodiment, the selection circuit 420 is a multiplexer array.Alternatively, the selection circuit may be other circuitry inside oroutside the capacitance sensor 201 to select the sensor element(s) to bemeasured.

In another embodiment, the capacitance sensor 201 may be used to measurecapacitance on all or less than all of the sensor elements of the touchpanel 410. Alternatively, multiple capacitance sensors 201 may be usedto measure capacitance on all or less than all of the sensor elements ofthe touch panel 410. In one embodiment, the selection circuit 420 isconfigured to connect the sensor elements that are not being measured tothe system ground. This may be done in conjunction with a dedicated pinin the GPIO port 207.

In one embodiment, the processing device 210 further includes a decisionlogic block 402. The operations of decision logic block 402 may beimplemented in firmware; alternatively, it may be implemented inhardware or software. The decision logic block 402 may be configured toreceive the digital code or counts from the capacitance sensor 201, andto determine the state of the touch panel 410, such as whether aconductive object is detected on or in proximity to the touch panel 410,which button has been pressed on the touch panel 410, or the like.

In another embodiment, instead of performing the operations of thedecision logic 402 in the processing device 210, the processing device201 may send the raw data to the host 250, as described above. Host 250,as illustrated in FIGS. 4A and 4B, may include decision logic 451. Theoperations of decision logic 451 may also be implemented in firmware,hardware, and/or software. Also, as described above, the host mayinclude high-level APIs in applications 452 that perform routines on thereceived data, such as compensating for sensitivity differences, othercompensation algorithms, baseline update routines, start-up and/orinitialization routines, interpolations operations, scaling operations,or the like. The operations described with respect to the decision logic402 may be implemented in decision logic 451, applications 452, or inother hardware, software, and/or firmware external to the processingdevice 210.

In another embodiment, the processing device 210 may also include anon-capacitance sensing actions block 403. This block may be used toprocess and/or receive/transmit data to and from the host 250. Forexample, additional components may be implemented to operate with theprocessing device 210 along with the touch panel 410 (e.g., keyboard,keypad, mouse, trackball, LEDs, displays, or the like).

At startup (or boot) the sensor elements (e.g., capacitors 355(1)-(N))are scanned and the digital code or count values for each sensor elementwith no activation are stored as a baseline array (C_(P)). The presenceof a finger on the sensor element or in proximity to the sensor elementis determined by the difference in counts between a stored value for nosensor element activation and the acquired value with sensor elementactivation, referred to here as Δn. The sensitivity of a single sensorelement is approximately:

$\begin{matrix}{\frac{\Delta\; n}{n} = \frac{C_{F}}{C_{P}}} & (14)\end{matrix}$

The value of Δn should be large enough for reasonable resolution andclear indication of sensor element activation (e.g., button activation).This drives sensor element construction decisions. C_(F) should be aslarge a fraction of C_(P) as possible. Since C_(F) is determined byfinger area and distance from the finger to the sensor element'sconductive traces (through the over-lying insulator), the baselinecapacitance C_(P) should be minimized. The baseline capacitance C_(P)includes the capacitance of the sensor element pad plus any parasitics,including routing and chip pin capacitance.

In one embodiment, the first mode 430 is a normal mode of operation ofthe electronic device 400. In another embodiment, the first mode 430 isa “fine” measurement mode and is when the electronic device is active,as opposed to being in “sleep” mode (as described below). In oneembodiment, determination of which touch-sensor button of a touch panel410 is performed in the first mode, while determination of whether aconductive object is present in proximity to the device is performed inthe second mode. In one embodiment, the button-activation sensing isperformed in the first mode, and the proximity sensing is performed inthe second mode. In one embodiment, the processing device 210 isconfigured to transition from the second mode to the first mode when thepresence of the conductive object is detected in proximity to the devicein the second mode, and to transition from the first mode to the secondmode when the presence of the conductive object is not detected on thedevice for a period of time in the second mode.

FIG. 4B illustrates the electronic device 400 of FIG. 4A in a secondmode 440. In the second mode 440, the selection circuit 420 isconfigured to couple all of the sensor elements 355(1)-355(N) to thecapacitance sensor 201 using individual switches. Instead of measuringthe capacitance on each of the sensor elements individually as done inthe first mode 430, the capacitance sensor 201 collectively measures atotal aggregate capacitance on the coupled sensor elements 355(1)-355(N)in the second mode 440. For example, as illustrated in FIG. 4B, all thesensor elements 355(1)-(N) are selected (as indicated by the blacksensor elements of the touch panel 410), and coupled to the capacitancesensor 201 to collectively measure the capacitance on all the sensorelements 355(1)-355(N). The processing device 210 is configured toperform a single capacitance measurement on all the sensor elements355(1)-355(N) during each sensing interval when in the second mode 440.As described above, in the second mode, a determination of whether aconductive object is present in proximity to the device is performed inthe second mode, instead of making a determination as to which buttonhas been activated in the first mode. In one embodiment, the proximitysensing is performed in the second mode, and the button-activationsensing is performed in the first mode.

It should be noted that although the embodiments of FIGS. 4A and 4Billustrate all the sensor elements 355(1)-355(N) being coupled togetherduring the second mode 440, in other embodiments, a fraction of all thesensor elements 355(1)-355(N) may be coupled together during the secondmode 440.

The processing device 210 may be configured to individually measure acapacitance on each of the sensor elements 355(1)-355(N) of theelectronic device 400 in the first mode 430. The processing device 210may also be configured to couple a group of (e.g., all or a fraction of)the sensor elements 355(1)-(N), and collectively measure an aggregatecapacitance on the group of sensor elements in the second mode 440. Thegroup of sensor elements may be coupled together and the aggregatecapacitance measured when detecting a presence of a conductive object onthe sensor elements during the first mode 430. In one embodiment, if theno conductive object is detected on the device while individuallymeasuring the capacitance on each of the sensor elements, the processingdevice transitions from the first mode 430 to the second mode 440. Inone embodiment, the second mode 440 is a sleep mode (e.g., reduced powermode). In one embodiment, the electronic device 400 may be placed in the“sleep” mode when the conductive object is not present on the electronicdevice 400. In another embodiment, the electronic device 400 is placedin the “sleep” mode after a certain number of individual sensing cycleshave resulted in no conductive object being detected on the electronicdevice 400. During “sleep” mode (e.g., second mode 440), the electronicdevice 400 can periodically scan the group of coupled sensor elements todetermine if a conductive object is in proximity to the electronicdevice 400. When the electronic device 400 detects the presence of theconductive object in proximity to the device in the “sleep” mode (e.g.,conductive object is detected while collectively measuring a capacitanceon the group of sensor elements), the electronic device 400 may beplaced in a normal or active mode (e.g., first mode 430).

In one embodiment, the electronic device 400 continues to individuallymeasure the capacitance on each of the sensor elements and is placed inthe “sleep” mode (e.g., second mode 440) for a period of time when theconductive object is not present on the device during the first mode430. The electronic device 400 may be placed in the “sleep” mode (e.g.,second mode 440) after the electronic device 400 has not detected aconductive object on the device after a predetermined period of time.Alternatively, the electronic device 400 may be placed in the “sleep”mode after the electronic device 400 has not detected a conductiveobject on the device after a certain number, N, individual sensingcycles. Once the predetermined period of time has lapsed, the electronicdevice 400 transitions from the first mode 430 to the second mode 440.This may be done to conserve power consumption in the electronic device400.

In the second mode 440, the electronic device 400 collectively measuresa capacitance on the group of sensor elements after the period of timehas lapsed. If the electronic device 400 does not detect a presence of aconductive object in proximity to the device during the second mode 440,the electronic device 400 may sleep for another period of time. Afterthis period of time, the electronic device 400 wakes and collectivelymeasures a capacitance on the group of sensor elements to detect whethera conductive object is in proximity to the electronic device 400. Oncethe electronic device 400 detects a presence of the conductive object inproximity to the electronic device 400 during the second mode 440, theelectronic device 400 transitions to the first mode 430 to individuallymeasure a capacitance on each of the sensor elements to determine if theconductive object is present on one of the areas of the overlay thatcorrespond to a touch-sensor button.

In one embodiment, while in the second mode 440, the processing device210 performs a baseline measurement on the group of sensor elementsafter the group of sensor elements are coupled together. The baselinemeasurement may be representative of the capacitance on the group ofsensor elements when a conductive object is not in proximity to theelectronic device 400. The baseline measurement may be measured toaccount for parasitic capacitance in the device. The baselinemeasurement may be compared against the capacitance measurements madeduring the second mode 440. For example, when the group of sensorelements is subsequently measured, if the collectively measuredcapacitance on the group of sensor elements is greater than the baselinemeasurement, then a presence of a conductive object is detected on theelectronic device. If the collectively measured capacitance is greaterthan the baseline measurement, the electronic device 400 may transitionto the first mode 430 to individually measure a capacitance on each ofthe sensor elements.

In another embodiment, the collectively measured capacitance can becompared to a threshold above the baseline measurement. For example, ifthe collectively measured capacitance is greater than the thresholdabove the baseline measurement, then a conductive object is detected inproximity to the electronic device 400, and the electronic device 400can transition to the first mode 430 to individually measure thecapacitance on each of the sensor elements. Conversely, if thecollective measured capacitance is less than the baseline measurement orless than the threshold above the baseline measurement, then a presenceof a conductive object is not detected in proximity to the electronicdevice 400, and the electronic device 400 remains in the second mode440. The electronic device 400 may be placed in the “sleep” mode for aperiod of time if the collectively measured capacitance on the groupsensor elements is equal to or less than the baseline measurement or thethreshold above the baseline measurement.

In one embodiment, the electronic device 400 transitions from the firstmode 430 to the second mode 440 when the presence of the conductiveobject is not detected in proximity to the sensor elements whileindividually measuring the capacitance on each of the sensor elements inthe first mode 430. In another embodiment, the electronic device 400transitions from the second mode 440 to the first mode 430 when thepresence of the conductive object is detected in proximity to the groupof sensor elements while collectively measuring the capacitance on thegroup of sensor elements in the second mode 440. As described above, thegroup of sensor elements may include all or a fraction of the sensorelements 355.

FIG. 4C illustrates another embodiment of the electronic device of FIG.4A in a second mode 450. The second mode 450 is similar to the secondmode 440 described with respect to FIG. 4B, except in the second mode450, not only are all the sensor elements 355(1)-355(N) selected (asindicated by the black sensor elements of the touch panel 41) andcoupled to the capacitance sensor 201, but the ground conductor 454 isalso coupled to the capacitance sensor 201 with the sensor elements355(1)-355(N) to collectively measure the capacitance on the coupledsensor elements and ground conductor 454. The ground conductor 454 isdisposed to partially or completely surround at least one of the sensorelements of the touch panel 410. In another embodiment, the groundconductor 454 is a ground plane disposed to surround each of the sensorelements 355(1)-355(N), as illustrated in FIG. 4C. Alternatively, groundconductor may be separate ground conductors that are separately disposedon the touch panel 410, but include ground traces coupled together toone pin of the processing device via ground trace 455. The groundconductor 454 may have a “fillfactor” of 100%—meaning that the groundconductor 454 is a continuous sheet—or the fillfactor may be lessthrough using a technique such as cross-hatching. The benefit of using across-hatching technique may be to reduce the parasitic capacitance ofthe conductor, thereby increasing the size of the signal (change incapacitance) when expressed as a ratio to the “static” capacitance(i.e., capacitance in the absence of a conductive object). Theprocessing device 210 is configured to perform a single capacitancemeasurement on all the sensor elements 355(1)-355(N) and the groundconductor 454 during each sensing interval when in the second mode 450.As described above, in the second mode, a determination of whether aconductive object is present in proximity to the device is performed inthe second mode, while a determination is made as to which button hasbeen activated in the first mode. In the first mode 430, the groundconductor 454 may be coupled to a ground of the processing device 210(e.g., via selection circuit 420), for example using the dedicated pinin the GPIO port 207, whereas in the second mode, the ground conductor454 is coupled to the other sensor elements (e.g., via selection circuit420), and is used as a sensor element to detect a conductive object inproximity to the electronic device 400. In one embodiment, the proximitysensing is performed in the second mode, and the button-activationsensing is performed in the first mode.

It should be noted that although the embodiments of FIG. 4C illustrateall the sensor elements 355(1)-355(N) being coupled together during thesecond mode 450, in other embodiments, a fraction of all the sensorelements 355(1)-355(N) may be coupled together with the ground conductor454 during the second mode 450.

It should also be noted that although the embodiments of FIG. 4Cillustrate the ground conductor 454 as being coupled to the sensorelements 355(1)-355(N), in other embodiments, other conductive materialmay be coupled to the sensor elements 355(1)-355(N) for purposes ofproximity detection. For example, in one embodiment, the conductivematerial of a housing of the electronic device, such as a metal case,metal used to support the electronic device, metal used forradio-frequency (RF) shielding, metal on the surface of the inside oroutside of the housing, or the like, is coupled to capacitance sensor201 along with group of sensor elements 355(1)-355(N) (e.g., all of or afraction of all the sensor elements) to detect a presence of aconductive object in proximity to the electronic device.

FIG. 5 illustrates a block diagram of one embodiment of an electronicdevice 500 including a processing device 210 that includes capacitancesensors 201 for measuring the capacitance on a slider 230. Theelectronic device 500 is similar to the electronic device 400, exceptthe processing device 210 is coupled to the slider 230 via the selectioncircuit 420, instead of the touch panel 410.

The slider 230 of FIG. 5 includes multiple sensor elements555(1)-555(N), where N is a positive integer value that represents thenumber of sensor elements. In one embodiment, the slider 230 may be asingle-dimension sensor array including the sensor elements555(1)-555(N). The single-dimension sensor array may provide output datato the analog bus 401 of the processing device 210 (e.g., via lines 231of FIG. 2). The slider 230 may be used for control requiring gradual ordiscrete adjustments. Examples include a lighting control (dimmer),temperature control, volume control, graphic equalizer, and speedcontrol. Slider controls may also be used for scrolling functions inmenus of data. These sensor elements may be mechanically adjacent to oneanother. Activation of one sensor element may result in partialactivation of physically adjacent sensor elements. The actual positionin the sliding sensor element is found by computing the centroidlocation of the set of sensor elements activated, as described below.

The decision logic block 402 may be configured to receive the digitalcode or counts from the capacitance sensor 201, and to determine thestate of the slider 230, such as whether a conductive object is detectedon the slider 230, such as which sensor element has been pressed,whether the conductive object is detected in proximity to the device,where the conductive object was detected on the slider 230 (e.g.,determining the X-, Y-coordinates of the presence of the conductiveobject), determining absolute or relative position of the conductiveobject, whether the conductive object is performing a pointer operation,whether a gesture has been recognized on the slider 230 (e.g., click,double-click, movement of the pointer, scroll-up, scroll-down,scroll-left, scroll-right, step Back, step Forward, tap, push, hop,zigzag gestures, et), or the like.

As described above, the selection circuit 420 is configured to coupleeach of the sensor elements to the capacitance sensor 201 of theprocessing device either individually for sequential measurements of thesensor elements in the first mode 430 or collectively for measurementsof the coupled sensor elements in the second mode 440 or 450.Alternatively, the sensor elements and the ground conductor may becoupled together for collectively measuring the capacitance. Forexample, as illustrated in FIG. 5, half of the sensor elements555(1)-555(N) are selected (as indicated by the black sensor elements ofthe slider 230) in the second mode 440, and coupled to the capacitancesensor 201 to measure the aggregate capacitance on the coupled sensorelements. However, in the first mode 430, each of the sensor elements555(1)-555(N) are sequentially selected and coupled to the capacitancesensor 201 of the processing device 210 to individually measure thecapacitance on each of the sensor elements 555(1)-555(N). Alternatively,a ground conductor may be coupled to the capacitance sensor 201 alongwith a group of (e.g., all or a fraction of all) the coupled sensorelements during the second mode 450. The processing device 210 isconfigured to perform a capacitance measurement on each of the sensorelements 555(1)-555(N) during each sensing interval when in the firstmode 430, and to perform a single capacitance measurement on the coupledsensor elements 555(1)-555(N) (e.g., half of the sensor elements) duringeach sensing interval when in the second mode 440 or 450.

It should be noted that although the embodiments of FIG. 5 illustratehalf of the sensor elements 555(1)-555(N) being coupled together duringthe second mode 440, in other embodiments, other fractions or all of thesensor elements 555(1)-555(N) may be coupled together during the secondmode 440 or 450. Coupling less than all of the sensor elements (e.g., afraction of all the sensor elements) in the second mode 440 may have theadvantage of reducing the background parasitic capacitance to ground inthe electronic device 500, and thus reduce the time taken to make thesingle measurement in the second mode 440, as compared to coupling allthe sensor elements, and thus further reduce the sleep current.

FIG. 6 illustrates a block diagram of one embodiment of an electronicdevice 600 including a processing device 210 that includes twocapacitance sensors 201 for measuring the capacitance on a sensor array610. The electronic device 600 is similar to the electronic devices 400and 500, except the processing device 210 is coupled to the sensor array610 using two selection circuits 420 and 620 and two capacitance sensors201. In one embodiment, the sensor array 610 is implemented in thetouch-sensor pad 220, as described with respect to FIG. 2.Alternatively, the sensor array 610 may be implemented in othercapacitance sensing devices.

In this embodiment, the sensor array 610 is a two-dimension sensor arrayincluding the sensor elements 655(1)-655(N), where N is a positiveinteger value that represents the number of sensor elements of thetwo-dimension sensor array. The two-dimension sensor array 610 mayprovide output data to the analog bus 401 of the processing device 210(e.g., via bus 221).

The sensing array 610 may be used for similar operation as describedabove with respect to the touch-sensor pad 220. The decision logic block402 may be configured to receive the digital code or counts from thecapacitance sensor 201, and to determine the state of the sensor array610, such as whether a conductive object is detected on the sensor array610, whether a conductive object is detected in proximity to the sensorarray 610, which sensor element of the sensor array 610 has beenpressed, where the conductive object was detected on the sensor array610 (e.g., determining the X-, Y-coordinates of the presence of theconductive object), determining absolute or relative position of theconductive object, whether the conductive object is performing a pointeroperation, whether a gesture has been recognized on the sensor array 610(e.g., click, double-click, movement of the pointer, scroll-up,scroll-down, scroll-left, scroll-right, step Back, step Forward, tap,push, hop, zigzag gestures, etc), or the like.

As described above, the selection circuit 420 is configured to coupleeach of the sensor elements to the capacitance sensor 201 of theprocessing device either individually for sequential measurements of thesensor elements in the first mode 430 or collectively for measurementsof the coupled sensor elements in the second mode 440 or 450. In anotherembodiment, the selection circuits 420 and 620 are configured to coupleeach of the sensor elements to the capacitance sensors 201 as sets ofsensor elements, such as a row or column of sensor elements. Theselection circuits 420 and 620 are configured to substantiallysimultaneously measure two sets of sensor elements at a time. Forexample, as illustrated in FIG. 6, a first row 601 and a first column602 are selected in the first mode 430, and coupled to the capacitancesensors 201, respectively, to individually measure the capacitance onthe first row and the first column of sensor elements. After thecapacitance has been measured on the first row 601 and first column 602,the selection circuits 420 and 620 each open the switch that connectsthe respective capacitance sensor 201 to the first row 601 and firstcolumn 602, and closes another switch that connects the respectivecapacitance sensor 201 to a subsequent row and a subsequent column,respectively. This is repeated to individually measure the capacitanceon each of the rows and each of the columns of the sensor array 610during the first mode 430. Alternatively, a ground conductor may becoupled to one of the capacitance sensors 201 along with a group of(e.g., all or a fraction of all) the coupled sensor elements during thesecond mode 450. The processing device 210 is configured to perform acapacitance measurement on each of the rows and columns during eachsensing interval when in the first mode 430. However, in the second mode440 or 450, all of the rows are coupled together to collectively measurean aggregate capacitance on the rows of the sensor array 610. Similarly,in the second mode 440 or 450, all of the columns are coupled togetherto collectively measure an aggregate capacitance on the columns of thesensor array 610. In one embodiment, the processing device 210 isconfigured to perform a single capacitance measurement on all the rowsof the sensor array 610 during each sensing interval when in the secondmode 440 or 450. In another embodiment, the processing device 210 isconfigured to perform a single capacitance measurement on all thecolumns of the sensor array 610 during each sensing interval when in thesecond mode 440 or 450. Alternatively, the processing device 210 isconfigured to perform both measurements of the all the rows and all thecolumns during each sensing interval when in the second mode 440.

It should be noted that although the embodiments of FIG. 6 illustrateall of the rows or all of the columns of the sensor array 610 beingcoupled together during the second mode 440, in other embodiments,fractions of all of the rows or fractions of all of the columns may becoupled together during the second mode 440. For example, half of thecolumns are coupled together and coupled to the first capacitance sensor201, and half of the rows are coupled together and coupled to the secondcapacitance sensor 201. Coupling less than all of the rows and/orcolumns (e.g., a fraction of all the rows or columns of sensor elements)in the second mode 440 or 450 may have the advantage of reducing thebackground parasitic capacitance to ground in the electronic device 600,and thus reduce the time taken to make the capacitance measurement(s) inthe second mode 440 or 450, as compared to coupling all the rows and/orall the columns of sensor elements.

The sensor array may be a grid-like pattern of sensor elements (e.g.,capacitive elements) used in conjunction with the processing device 210to detect a presence of a conductive object, such as a finger, to aresolution greater than that which is native. The touch-sensor padlayout pattern may be disposed to maximize the area covered byconductive material, such as copper, in relation to spaces necessary todefine the rows and columns of the sensor array.

In applications for touch-sensor sliders (e.g., sliding sensor elements)and touch-sensor pads it is often necessary to determine finger (orother capacitive object) position to greater resolution than the nativepitch of the individual sensor elements. The contact area of a finger ona sliding sensor element or a touch-pad is often larger than any singlesensor element. In one embodiment, in order to calculate theinterpolated position using a centroid, the array is first scanned toverify that a given sensor element location is valid. The requirement isfor some number of adjacent sensor element signals to be above a noisethreshold. When the strongest signal is found, this signal and thoseimmediately adjacent are used to compute a centroid:

$\begin{matrix}{{Centroid} = \frac{{n_{i - 1} \cdot \left( {i - 1} \right)} + {n_{i}i} + {n_{i + 1} \cdot \left( {i + 1} \right)}}{n_{i - 1} + {n_{i}i} + n_{i + 1}}} & (15)\end{matrix}$

The calculated value may be fractional. In order to report the centroidto a specific resolution, for example a range of 0 to 100 for 12 sensorelements, the centroid value may be multiplied by a calculated orpredetermined scalar. It may be more efficient to combine theinterpolation and scaling operations into a single calculation andreport this result directly in the desired scale. This may be handled inthe high-level APIs. Alternatively, other methods may be used tointerpolate the position of the conductive object.

FIG. 7A illustrates a back-side view of one embodiment of a touch panel700 having two touch-sensor buttons 701 and 702 and a ground conductor703 surrounding the two touch-sensor buttons 701 and 702. Thetouch-sensor buttons 701 and 702 each include a sensor element 704 and705, respectively, which are used by the processing device 210 to detectthe presence of the conductive object on the touch-sensor buttons 701and 702. The ground conductor 703 may be coupled to a ground of theprocessing device while detecting a presence of the conductive object ontouch panel 700, such as in the first mode 430. However, in the secondmode the ground conductor 703 may be coupled to the sensor elements 704and 705, and a collective capacitance is measured on the groundconductor 703, and the sensor elements 704 and 705 to detect a presenceof the conductive object in proximity to the touch panel 700, such as inthe second mode 450. The processing device 210 may be configured tomeasure a capacitance on each of the sensor elements 704 and 705individually in the first mode 430, and to measure a capacitance on allof the sensor elements 704 and 705 collectively in the second mode 440.Alternatively, the processing device 210 may be configured to measure acapacitance on each of the sensor elements 704 and 705 individually inthe first mode 430, and to measure a capacitance on all of the sensorelements 704 and 705 and the ground conductor 703 collectively in thesecond mode 450. If the capacitance measured on either of the sensorelements 704 or 705 is greater than a baseline measurement (or athreshold above the baseline measurement), respectively, thetouch-sensor button 701 or 702 is registered as having a buttonactivation. If the capacitance measured on all of the sensor elements704 and 705, and the ground conductor 703 is greater than a baselinemeasurement (or a threshold above the baseline measurement), the touchpanel 700 is registered as having a proximity event.

In this embodiment, the ground conductor 703 is disposed to surround thesensor elements 704 and 705 that correspond to the touch-sensor buttons701 and 702, respectively. The touch panel 700 also includes aninsulation area 706 of non-conductive material. The insulation area 706is disposed between the ground conductor 703 and the other sensorelements 704 and 705. In particular, the insulation area 706 is disposedso that the ground conductor 703 is disposed to substantially surroundthe sensor elements 704 and 705, instead of completely surrounding thesensor elements. Alternatively, the ground conductor 703 may be disposedto partially or completely surround the sensor elements 704 and 705.

In this embodiment, the two sensor elements (704 and 705) are coupled tothe processing device 210 (e.g., via capacitance sensing pins 306). Inone embodiment, the processing device 210 is configured to measure acapacitance on each of the sensor elements 704 and 705, individually,and a collective capacitance on all the sensor elements (e.g., bycoupling the two sensor elements 704 and 705 together when measuring).In another embodiment, the processing device 210 is configured tomeasure a capacitance on each of the sensor elements 704 and 705,individually, and a collective capacitance on all two of the sensorelements and the ground conductors 703 (e.g., by coupling the two sensorelements 704 and 705 and the ground conductors 703 together whenmeasuring).

FIG. 7B illustrates a back-side view of one embodiment of a touch panel750 having three touch-sensor buttons 751, 752, and 753, and threeground conductors 753 each surrounding one of the three touch-sensorbuttons. The touch panel 750 is similar to the touch panel 700 of FIG.7A, except the ground conductors 753 are separate conductors that areeach disposed to surround one of the three sensor elements, instead ofone single ground conductor, and the touch panel 750 includes threetouch-sensor buttons, instead of two. In this embodiment, the groundconductor 753 is of similar dimension and shape as the sensor elements754, 755, and 756. Alternatively, the ground conductor 753 may havedissimilar dimensions and/or dissimilar shapes as the sensor elements754, 755, and 756.

In this embodiment, the three sensor elements (754, 755, and 756) arecoupled to the processing device 210 (e.g., via capacitance sensing pins306). In one embodiment, the processing device 210 is configured tomeasure a capacitance on each of the sensor elements 754, 755, and 756,individually, and a collective capacitance on all the sensor elements(e.g., by coupling the three sensor elements 754, 755, and 756 togetherwhen measuring). In another embodiment, the processing device 210 isconfigured to measure a capacitance on each of the sensor elements 754,755, and 756, individually, and a collective capacitance on all three ofthe sensor elements and the ground conductors 753 (e.g., by coupling thethree sensor elements 754, 755, and 756 and the ground conductors 753together when measuring).

The sensor elements of FIG. 7A have been illustrated as rings, having anouter ring of conductive material with an inside of non-conductivematerial. This is commonly done to allow LED or other backlightingmethods to pass through the capacitance sensors to illuminate the touchpanel user interface graphics (e.g. key legends). Alternatively, thesensor elements may be other shapes, such as solid circles (illustratedin FIG. 7B), square, rectangular, semi-circle, oval, diamond, hexagonal,pentagonal, octagonal, or the like. Transparent conductive materialssuch as Indium Tin Oxide (ITO), organic polymers such asPolyethylenedioxythiophene (PEDOT) Polypyrrole, Polyaniline or the like,or other transparent polymers that allow backlight to propagate throughthem may be used without the need for cutouts as described above.

FIG. 7C illustrates a front-side view of one embodiment of a touch panel775 having four touch-sensor buttons 780 in a first zone and fourtouch-sensor buttons 780 in a second zone, and a ground conductor 783surrounding the eight touch-sensor buttons 780. The touch panel 775 issimilar to the touch panel 700 of FIG. 7A, except the touch panel 775has eight touch-sensor buttons that are disposed in zones. In thisembodiment, the ground conductor 783 is disposed to surround all of theeight touch-sensor buttons 780. However, in the second mode 440 or 450,the sensor elements 778 are coupled together in two zones. Four of thesensor elements 778 are coupled together in a first zone 776, and fourof the sensor elements 778 are coupled together in a second zone 777.The first zone 776 of sensor elements 778 are coupled to the processingdevice 210 via one capacitance sensing pin 306, and the second zone 777of sensor elements 778 are coupled to the processing device 210 viaanother capacitance sensing pin 306. In one embodiment, the processingdevice 210 is configured to measure a capacitance on each of the sensorelements 778, individually, and a collective capacitance on the coupledsensor elements of the first zone 776 and of the second zone 777 (e.g.,by coupling the four sensor elements 778 of each zone together whenmeasuring the respective zones). In another embodiment, the processingdevice 210 is configured to measure a capacitance on each of the sensorelements 778, individually, and a collective capacitance on the firstzone 776 and the ground conductor 783 (e.g., by coupling the four sensorelements 778 of the first zone 776 and the ground conductor 783 togetherwhen measuring), and a collective capacitance on the second zone 777 andthe ground conductor 783 (e.g., by coupling the four sensor elements 778of the second zone 777 and the ground conductor 783 together whenmeasuring). Alternatively, the ground conductor 783 is coupled to onlyone of the zones when measuring that particular zone, and not coupled tothe other zone when measuring the other zone. In another embodiment, twoseparate ground conductors are used in each of the zones. The first zone776 of sensor elements 778 uses one of the ground conductors, and thesecond zone 777 of sensor elements 778 uses the other ground conductorfor proximity sensing. The two ground conductors are coupled togetherand to the ground of the processing device 210 for button-activationsensing. It should be noted that in other embodiments, the number ofzones and/or the number of sensor elements in each zone may be more orless than four.

FIG. 8 illustrates a graph of a sensitivity of a single touch-sensorbutton. Graph 800 includes the counts 852 as measured on a singletouch-sensor button for “no presence” 850 on the touch-sensor button,and for a “presence” 851 on the touch-sensor button. In one embodiment,when the “presence” 851 is detected, a button activation is determined.In another embodiment, when the “presence” 851 is detected, a proximityevent is determined. The “No presence” 850 occurs when the touch paneldoes not detect the presence of the conductive object. The “No presence”850 is detected between a range of noise. The range of noise may includea positive noise threshold 847 and a negative noise threshold 848. Solong as the counts 852 are measured as being between the positive andnegative thresholds 847 and 848, the touch panel detects “no presence”850. The “Presence” 851 is when the touch panel detects the presence ofthe conductive object (e.g., finger). The “Presence” 851 is detectedwhen the counts 852 are greater than a presence threshold 845. Thepresence threshold 845 indicates that a presence of a conductive objectis detected on the touch panel during touch-activation sensing. Thesensitivity 849 (Cf/Cp) of the single button operation is such that whenit detects the presence of the conductive object, the capacitancevariation (Δn) is above the presence threshold 845. The sensitivity 849may have a range, sensitivity range 846. Sensitivity range 846 may havea lower and upper limit or threshold. The lower threshold is equal to orgreater than the presence threshold 845, allowing a “presence” 851 to bedetected on or in proximity to the touch-sensor button. The touch panelmay be configured such that there is a design margin between thepresence threshold 845 and the positive noise threshold 847. Thesensitivity range 846 is based on the surface area of the touch-sensorbutton, as well as other factors.

Although FIG. 8 is usually representative of the sensitivity of a singletouch-sensor button, FIG. 8 may also illustrate the sensitivity of agroup of coupled sensor elements. It should also be noted that thevalues of parameters in the graph of FIG. 8 may be different for thedifferent configurations. For example, in scanning a sensor elementindividually, the presence threshold 845 may be set to have an arbitrarycount of 100 counts, based on factors such as scan speed, surface area,and the like. It should be noted in this embodiment, separate baselinemeasurement can be made for each of the sensor elements that are beingmeasured individually, and the capacitance on a particular sensorelement is compared against a presence threshold, such as the presencethreshold 845, to determine if the particular sensor element has beenactivated. However, using the same hardware (e.g., sensor elements,ground conductors, capacitance sensing pins, processing device, and thelike), in scanning the group of coupled sensor elements, the presencethreshold may be set to have a similar or dissimilar presence threshold,for example, a lower count than the 100 counts used in the otherconfiguration. Alternatively, other thresholds may be set for thedifferent configurations, such as for the button-activation sensing orthe proximity sensing.

In one embodiment, the counts 852 of graph 800 are representative of thecapacitance measured in the first mode while individually measuring thecapacitance on a single sensor element to detect a presence of aconductive object on a device (e.g., button-activation sensing). In thisembodiment, a button activation may occur when the counts 852 are abovethe presence threshold 845. In an embodiment having ten separatebuttons, the capacitance is measured individually on each sensorelement, such as illustrated on one sensor element in FIG. 8, and abutton activation is determined for each of the sensor elements todetermine whether any of the buttons have been activated by comparingthe counts 852 to the presence threshold 845.

In another embodiment, the counts 852 of graph 800 are representative ofthe capacitance measured in the second mode while collectively measuringthe capacitance on a group of coupled sensor elements to detect apresence of the conductive object in proximity to the device (e.g.,proximity event). For example, the counts 852 are representative of thecapacitance measured on all, or a fraction of all the sensor elementscoupled together during the second mode. In this embodiment, a proximityevent occurs when the counts 852 are above the presence threshold 845.In an embodiment having ten buttons, all ten, or a fraction of the tensensor elements are coupled together, and the capacitance, asrepresented by the counts 852 in FIG. 8, on the ten sensor elements isused to determine a proximity event for the group of coupled sensorelements.

In another embodiment, the counts 852 of graph 800 are representative ofthe capacitance measured in the second mode while collectively measuringthe capacitance on a group of sensor elements and a ground conductorthat are coupled together. A separate baseline measurement may be made,and a different presence threshold may be set for this configuration.

It should be noted that the same hardware (e.g., sensor elements, groundconductors, capacitance sensing pins, processing device, and the like)is used to detect a button activation and a proximity event. For thedifferent configurations, the processing device may be tuned to measurea capacitance for the different configurations and determine a buttonactivation or a proximity event based on the measured capacitance.

FIG. 9 illustrates a top-side view and a bottom-side view of oneembodiment of a case 910 of a mobile handset 900 having two touch-sensorbuttons 901 and 902 and a ground conductor 903 for button-activationsensing and proximity sensing. The top-side view illustrates the case910 (e.g., faceplate or outside housing of the mobile handset 90), whichincludes openings for a display 920, a camera 930, and touch-sensorbuttons 901 and 902. The display 920 may be configured to display text,images, and/or video. The camera 930 may be configured to capture imagesand/or video. The touch-sensor buttons 901 and 902 are configured to beinput buttons for the mobile handset 900. The camera 930 and display 920are known by those of ordinary skill in the art, and accordingly, adetailed description regarding their operation has not been included.The touch-sensor buttons 901 and 902 operate similarly to thetouch-sensor buttons described herein. The back-side view illustratesthe case 910 to which the processing device 210, sensor elements 904 and905, and ground conductor 903 are coupled. It should be noted that themobile handset 900 may include additional components that are known bythose of ordinary skill in the art, and may include less components thanillustrated in FIG. 9, such as the display 920 or camera 930.

Sensor elements 904 and 905 and ground conductor 903 are coupled to theprocessing device 210 (e.g., via capacitance sensing pins 306 ofprocessing device 210), using for example, wires or conductive traces.In one embodiment, the processing device 210, sensor elements 904 and905, and ground conductor 903 are disposed on a common substrate, forexample, a substrate of a printed circuit board. Alternatively, theprocessing device 210, sensor elements 904 and 905, and ground conductor903 are disposed in other configurations, such as the processing deviceon one substrate and the sensor elements (904, 904, and 903) aredisposed on another substrate or directly on the case 910.

Although ground conductor 903 is illustrated as a sensor element havingsimilar shape to the sensor elements 904 and 905, the ground conductor903 may have other dimensions and/or shapes than the sensor elements 904and 905. Similarly, although ground conductor 903 is illustrated as asensor element disposed between the sensor elements 904 and 905, theground conductor 903 may be disposed in other configurations, such asdisposed to partially surround, substantially surround, or completelysurround the sensor elements 904 and 905.

Using the embodiment described herein, as a conductive object is placedin proximity to the mobile handset 900, the processing device 210 maydetect the presence of the conductive object, as well as detect theconductive object on the mobile handset 900, such as to detect buttonactivations on touch-sensor buttons 901 and 902.

In one embodiment, the mobile handset 900 includes an operation (e.g.,turn on display of camera 930 or a backlight display associated with thetouch-sensor buttons 901 and 902) that can be activated by detecting theconductive object in proximity to the mobile handset 900. The proximitysensing may be performed by coupling both of the sensor elements 904 and905 together via a selection circuit of the processing device 210.Alternatively, the proximity sensing may be performed by coupling bothof the sensor elements 904 and 905, and the ground conductor 903together via the selection circuit. Using the ground conductor 903, theeffective surface area of the sensor elements (e.g., 904, 905, and 903)used for proximity sensing is larger than the surface area of sensorelements 904 and 905 for proximity detection, allowing the mobilehandset 900 to be tuned to respond to detecting a conductive object inproximity to the mobile handset 900, as well as tuned to respond todetecting the conductive object on the touch-sensor buttons 901 and 902.

In this embodiment, the ground conductor 903 is located between thesensor elements 904 and 905 of the touch-sensor buttons 901 and 902,however, alternatively, the ground conductor 903 may be other sizes andbe disposed in other locations for both proximity sensing andbutton-activation sensing. For example, a ground plane may be disposedto at least partially surround the sensor elements 904 and 905. Inanother embodiment, the case 910 includes conductive material, such asmetal on the faceplate 910, metal on electromechanical buttons of themobile handset 900, or the like, that is coupled to the processingdevice 210 for proximity sensing. In this embodiment, forbutton-activation sensing, the conductive material that is coupled tothe processing device for proximity sensing is not coupled to theprocessing device 210 when individually measuring the capacitance oneach of the touch-sensor buttons 901 and 902.

In one embodiment, the ground conductor 903 and sensor elements 904 and905 are configured to detect a presence of a conductive object (e.g.,finger) in proximity to the mobile handset 900 within approximately sixto eight inches (6-8 in) of the touch-sensor button. Alternatively, theground conductor 903 may be configured to detect a presence of aconductive object within less than six inches or further away than eightinches.

Although the embodiments of FIG. 9 have been illustrated as beingimplemented in a mobile handset 900, alternatively, the embodiments maybe implemented in touch panel of a TV, a DVD player, a VCR, a DVR, areceiver, a computer, a radio, a light switch, a fan switch, industrialequipment, or the like. For example, a DVR front panel may include thetouch panel including multiple touch-sensor buttons. The touch panel mayhave a backlight that is illuminated when activated. The backlight ofthe touch panel shows where the touch-sensor buttons are located, aswell as any text associated with the touch-sensor buttons or the touchpanel. When not activated, since the backlight is not illuminated, thetouch-sensor buttons and/or text are not displayed on the touch panel.Using the embodiments described herein, when a conductive object isdetected in proximity to the touch panel, the backlight is activated,exposing the location of the touch-sensor buttons, and the associatedtext or symbols of the touch-sensor buttons. With the touch paneldisplay activated, the user may select a touch-sensor button, and thetouch panel detects a touch activation when the user presses thetouch-sensor button. Alternatively, the embodiments described herein maybe implemented as touch-sensor buttons, touch-sensor sliders,touch-sensor pads in mobile devices, such as PDAs, mobile handsets(e.g., cellular phones or other mobile phones), handheld multi-mediadevices, handheld video player, handheld gaming device, radio receivers,personal music players, or the like, or in other electronic devices,such as notebook or desktop computers, kiosks, keyboards, remotecontrols, monitors, control panels of household appliances(refrigerators, freezers, ovens, microwave ovens, toasters, washer,dryers, dishwashers, or the like).

FIG. 10 illustrates one embodiment of a selection circuit 420 coupled toan analog bus 401 for measuring capacitance on the sensor elements 904and 905 and the ground conductor 903. As previously described, theselection circuit 420 is coupled to the sensor elements (e.g., 904, 905,and ground conductor 903) via capacitance sensing pins 306, currentsource 352, reset switch 354, and a comparator 353 (not illustrated) viaanalog bus 401. The selection circuit 420 may be configured tosequentially select a sensor element of the multiple sensor elements 904and 905 to provide the charge current and to measure the capacitance ofeach sensor element 904 and 905, individually. This may be done in thefirst mode 430. In the second mode 440, the sensor elements 904 and 905are selected and coupled together to provide the charge current and tomeasure a collective capacitance on the coupled sensor elements 904 and905. In another embodiment, in the second mode 450, the sensor elements904 and 905, and the ground conductor 903 are selected and coupledtogether to provide the charge current and to measure a collectivecapacitance on the coupled sensor elements 904 and 905, and groundconductor 903.

It should be noted that although the selection circuit 420 isillustrated and described with respect to a relaxation oscillator havingthe current source 352, reset switch 354, and comparator 353,alternatively, the selection circuit 420 is implemented with other typesof circuits for measuring capacitance, such as the circuit 375 thatincludes the sigma-delta modulator 360, or other types of capacitancemeasuring circuits, such as current versus voltage phase shiftmeasurement, resistor-capacitor charge timing, capacitive bridgedivider, charge transfer, sigma-delta modulators, charge-accumulationcircuits, or the like.

In one exemplary embodiment, the selection circuit 420 is a multiplexerarray of the relaxation oscillator 350 or circuit 375. Alternatively,selection circuit 420 may be other circuitry outside the relaxationoscillator 350 or circuit 375, or even outside the capacitance sensor201 to select the sensor element to be measured. The selection circuit420 may also be used to ground the sensor elements that are not beingmeasured. This may be done in conjunction with a dedicated pin in theGPIO port 207. The selection circuit 420 may also be used to couple allthe sensor elements 904, 905, and/or ground conductor 903 at the sametime. When the sensor elements 904, 905, and 903 are coupled togetherthe processing device 210 may be configured to measure the capacitanceon all three sensor elements. Alternatively, the processing device 210may sequentially or simultaneously scan each of the sensor elementsindividually. The processing device 210 can select the sensor elements904, 905, and 903 using selection control lines 1001, 1002, and 1003,respectively.

FIG. 11 illustrates a flow chart of one embodiment of a method 1100 forbutton-activation sensing and proximity sensing. Method 1100 isinitialized in operation 1101, and once initialized, the device isplaced in the normal mode, operation 1102. The normal mode 1102 may bethe first mode 430, in which the device is configured to performbutton-activation sensing. In one embodiment, while in the normal mode,a presence of a conductive object is detected on a device byindividually measuring a capacitance on each of the sensor elements ofthe device. In normal mode, detection algorithms may be performed. Thedetection algorithms may include whether a presence of the conductiveobject is present on the device, which sensor element and correspondingbutton has been activated, the location of the presence of theconductive object on the device, whether a gesture is recognized, or thelike. In one embodiment, a button activation is determined when theconductive object is detected on a first sensor element using thecapacitance measured on the first sensor element. Upon determining thebutton activation, a button operation may be performed.

A timer may be set in the normal mode, and the method determines whetherthe timer has expired in operation 1103 without a button activationbeing detected. If the timer has not expired, the method continues innormal mode 1102. However, if the timer has expired in operation 1103without a button activation being detected, the method is placed in theproximity mode, operation 1104. The proximity mode may be the secondmode 440 or second mode 450, as described above, in which the device isconfigured to perform proximity sensing. In one embodiment, while in theproximity mode, a group of sensor elements (e.g., all of or a fractionof all of the sensor elements) are coupled together, and a presence of aconductive object is detected in proximity to the device by collectivelymeasuring a capacitance on the group of sensor elements of the device,operation 1105. In another embodiment, while in the proximity mode, aground conductor is coupled to the group of sensor elements whilecollectively measuring the capacitance on the coupled sensor elements todetect the presence of the conductive object in proximity to the device.It should be noted that the ground conductor is coupled to thecapacitance sensing pin of the processing device along with the sensorelements while collective measuring the capacitance for proximitysensing, and coupled to a ground of the processing device while thecapacitance is individually measured on each of the sensor elements forbutton-activation sensing in the normal mode. If in operation 1105, theconductive object is detected in proximity to the device, the method1100 returns to the normal mode in operation 1102, and may perform aproximity operation, such as activating a display. However, if theconductive object is not detected in proximity to the device, the methodremains in the proximity mode in operation 1104. In one embodiment, aproximity event is determined when the conductive object is detected inproximity to the device using the collective capacitance measured ongroup of sensor elements and/or the ground conductor. Upon determiningthe proximity event, an operation may be performed, such as activating adisplay.

In another embodiment, while in the proximity mode, a first group ofsensor elements are coupled together in a first zone (e.g., first zone776) of the device, and a second group of sensor elements are coupledtogether in a second zone (e.g., second zone 777) of the device. Thecollective capacitance is measured on each of the first and secondzones. Using the collective capacitance, the device determines a firstproximity event when the conductive object is detected in proximity tothe first zone of the device, and a second proximity event when theconductive object is detected in proximity to the second zone of thedevice. The first proximity event triggers a first operation, and thesecond proximity event triggers a second operation. The first and secondoperations may activate respective portions of a display. Alternatively,other types of operations may be performed in response the first andsecond proximity events.

FIG. 12 illustrates a flow chart of one embodiment of a method 1200 forcoupling a group of sensor elements together when in a reduced powermode. Method 1200 starts in operation 1201, and individually connectseach of the sensor elements to the processing device in turn, operation1202, and performs a baseline measurement for each of the sensorelements, operation 1203. The baseline measurement for each of thesensor elements is representative of the capacitance on each of thesensor elements while a conductive object is not present on the device(e.g., the particular sensor element). The method then measures acapacitance on each of the sensor elements in turn, operation 1204. Theprocessing device 210 then performs conductive object detectionalgorithms. The detection algorithms may include whether a presence ofthe conductive object is present on the device, which sensor element andcorresponding button has been activated, the location of the presence ofthe conductive object on the device, whether a gesture is recognized, orthe like. In one embodiment, each of the capacitances measured thesensor elements are compared with the respective baseline measurementfor the particular sensor element. The sensor element is activated whenthe capacitance is greater than the respective baseline measurement. Inanother embodiment, the sensor element is activated when the capacitanceis greater than a threshold (e.g., presence threshold 845) above thebaseline measurement.

The method 1200 then determines whether a conductive object detectionalgorithm detected the presence of the conductive object, operation1205. If the presence of the conductive object is detected in operation1205, the processing device 210 sends button press data to the host 250,operation 1206, and returns to measure a capacitance of each sensorelement in turn in operation 1202. However, if the presence of theconductive object is not detected in operation 1205, the processingdevice 210 connects all (or a fraction of all) of the sensor elementstogether, operation 1207. This may be done using the selection circuit420. After all (or a fraction of all) of the sensor elements are coupledtogether, a baseline measurement is performed, operation 1208. Thebaseline measurement is representative of the aggregate capacitance onthe coupled sensor elements when no conductive object is present on thedevice. The baseline measurement accounts for the parasitic capacitanceof the coupled sensor elements. Once the baseline measurement has beenperformed in operation 1208, the capacitance is collectively measured onthe coupled sensor elements, operation 1209. In one embodiment, thecoupled sensor elements include the sensor elements of the touch-sensorbuttons. In another embodiment, the coupled sensor elements include thesensor elements of the touch-sensor buttons, as well as a groundconductor.

The method 1200 then determines if the collective capacitance is greaterthan the baseline measurement performed in operation 1209, operation1210. In another embodiment, a threshold (e.g., presence threshold 845)above the baseline measurement may be used. If the collectivecapacitance is greater than the baseline measurement or the threshold(e.g., presence threshold 845) above the baseline measurement, themethod 1200 returns to measuring a capacitance of each of the sensorelements in turn of operation 1202. However, if the collectivecapacitance is not greater than the baseline measurement or thethreshold above the baseline measurement, the method 1200 places thedevice in the reduced power mode (e.g., “sleep” mode) for a period oftime (e.g., 100 ms), operation 1211. After the period of time haslapsed, the device wakes and measures the collective capacitance againin operation 1209. This process is repeated until a presence of aconductive object is detecting using the group of sensor elements. Oncethe conductive object is detected, then the method returns toindividually measuring each of the sensor elements.

In one embodiment, the method includes individually measuring acapacitance on each of the sensor elements of a touch-sensor device in afirst mode, and collectively measuring the capacitance on the group ofsensor elements in a second mode. The second mode may be a lower powermode than the first mode. The second mode includes a reduced power modethat allows the power in the device to be reduced as compared to whenthe device is in the first mode.

In another embodiment, the method includes individually measuring acapacitance on each of the sensor elements of a touch-sensor device. Themethod also includes coupling together a group of sensor elements, suchas all of or a fraction of all of the sensor elements of the device forproximity sensing. Once the group of sensor elements is coupledtogether, the method includes collectively measuring a capacitance onthe group of sensor elements. This may be done to reduce the amount ofpower consumption to determine if a conductive object is in proximity tothe device or not. If the device continues to determine that noconductive object is in proximity to the device when the sensor elementsare coupled together, the device can be placed in a reduced power modefor a period of time, periodically waking to make a coarse measurementof whether a conductive object is in proximity or not. This reduces thepower consumption of the device.

In another embodiment, the method includes transitioning from the secondmode to the first mode when the presence of the conductive object isdetected in proximity to the device in the second mode. The method mayalso include transitioning from the first mode to the second mode whenthe presence of the conductive object is not detected on the device fora period of time in the first mode.

Embodiments of the present invention, described herein, include variousoperations. These operations may be performed by hardware components,software, firmware, or a combination thereof. As used herein, the term“coupled to” may mean coupled directly or indirectly through one or moreintervening components. Any of the signals provided over various busesdescribed herein may be time multiplexed with other signals and providedover one or more common buses. Additionally, the interconnection betweencircuit components or blocks may be shown as buses or as single signallines. Each of the buses may alternatively be one or more single signallines and each of the single signal lines may alternatively be buses.

Certain embodiments may be implemented as a computer program productthat may include instructions stored on a machine-readable medium. Theseinstructions may be used to program a general-purpose or special-purposeprocessor to perform the described operations. A machine-readable mediumincludes any mechanism for storing or transmitting information in a form(e.g., software, processing application) readable by a machine (e.g., acomputer). The machine-readable medium may include, but is not limitedto, magnetic storage medium (e.g., floppy diskette); optical storagemedium (e.g., CD-ROM); magneto-optical storage medium; read-only memory(ROM); random-access memory (RAM); erasable programmable memory (e.g.,EPROM and EEPROM); flash memory; electrical, optical, acoustical, orother form of propagated signal (e.g., carrier waves, infrared signals,digital signals, etc.); or another type of medium suitable for storingelectronic instructions.

Additionally, some embodiments may be practiced in distributed computingenvironments where the machine-readable medium is stored on and/orexecuted by more than one computer system. In addition, the informationtransferred between computer systems may either be pulled or pushedacross the communication medium connecting the computer systems.

Although the operations of the method(s) herein are shown and describedin a particular order, the order of the operations of each method may bealtered so that certain operations may be performed in an inverse orderor so that certain operation may be performed, at least in part,concurrently with other operations. In another embodiment, instructionsor sub-operations of distinct operations may be in an intermittentand/or alternating manner.

In the foregoing specification, the invention has been described withreference to specific exemplary embodiments thereof. It will, however,be evident that various modifications and changes may be made theretowithout departing from the broader spirit and scope of the invention asset forth in the appended claims. The specification and drawings are,accordingly, to be regarded in an illustrative sense rather than arestrictive sense.

What is claimed is:
 1. A method, comprising: detecting a presence of aconductive object on a device by individually measuring a capacitancefor each of a plurality of sensor elements of the device; coupling agroup of sensor elements of the plurality of sensor elements together;conductively coupling a ground conductor to the group of coupled sensorelements; and measuring a single collective capacitance for the group ofcoupled sensor elements to detect a presence of the conductive object inproximity to the device by applying a signal to the group of coupledsensor elements while the group of coupled sensor elements isconductively coupled with the ground conductor.
 2. The method of claim1, further comprising: coupling the group of coupled sensor elements andthe ground conductor to a processing device while collectively measuringthe capacitance on the group of coupled sensor elements to detect thepresence of the conductive object in proximity to the device; andcoupling the ground conductor to a ground of the processing device whileindividually measuring the capacitance on each of the plurality ofsensor elements to detect the presence of the conductive object on thedevice.
 3. The method of claim 2, further comprising determiningactivation of a first sensor element of the plurality of sensor elementswhen the presence of the conductive object is detected on the firstsensor element of the device.
 4. The method of claim 3, furthercomprising: determining a button activation when the conductive objectis detected on the first sensor element using the individual capacitancemeasured on the first sensor element; determining a proximity event whenthe conductive object is detected in proximity to the device using thecollective capacitance on the group of coupled sensor elements and theground conductor; performing a first operation upon determining theproximity event; and performing a second operation upon determining thebutton activation.
 5. The method of claim 4, wherein performing thefirst operation comprises activating a display, and wherein performingthe second operation comprises performing a button operation.
 6. Themethod of claim 4, wherein determining the proximity event comprises:performing a first baseline measurement on the group of sensor elementswhile the group of sensor elements are coupled together, wherein thefirst baseline measurement is representative of the capacitance on thegroup of coupled sensor elements while a conductive object is not inproximity to the device; and comparing the capacitance measured on thegroup of coupled sensor elements with the first baseline measurement onthe group of coupled sensor elements while the group of sensor elementsare coupled together, wherein the proximity event is determined when thecapacitance measured on the group of coupled sensor elements is greaterthan the first baseline measurement, and wherein determining the buttonactivation comprises: performing a baseline measurement on each of theplurality of sensor elements while the plurality of sensor elements arenot coupled together, wherein the baseline measurements of each of theplurality of sensor elements are representative of the capacitance oneach of the plurality of sensor elements while a conductive object isnot present on the device; and comparing the capacitances on each of theplurality of sensor elements with the baseline measurements on each ofthe plurality of sensor elements while the plurality of sensor elementsare not coupled together, wherein the button activation is determinedwhen the capacitance on the first sensor element is greater than therespective baseline measurement of the first sensor element.
 7. Themethod of claim 1, wherein collectively measuring the capacitance on thegroup of coupled sensor elements is performed in a first mode, andwherein individually measuring the capacitance on each of the pluralityof sensor elements is performed in a second mode, and wherein the methodfurther comprises: transitioning from the first mode to the second modewhen the presence of the conductive object is detected in proximity tothe device in the first mode; and transitioning from the second mode tothe first mode when the presence of the conductive object is notdetected on the device for a period of time.
 8. The method of claim 1,wherein coupling the group of sensor elements comprises at least one ofcoupling all of the plurality of sensor elements together as the groupof sensor elements or coupling a fraction of the plurality of sensorelements together as the group of sensor elements.
 9. The method ofclaim 1, wherein coupling the group of sensor elements comprisescoupling the group of sensor elements as a first group of coupled sensorelements in a first zone of the device, and wherein the method furthercomprises: coupling a second group of sensor elements of the pluralityof sensor elements together in a second zone of the device; collectivelymeasuring a capacitance on each of the first and second groups ofcoupled sensor elements; determining a first proximity event when theconductive object is detected in proximity to the first zone of thedevice using the collective capacitance on the first group of coupledsensor elements; determining a second proximity event when theconductive object is detected in proximity to the second zone of thedevice using the collective capacitance on the second group of coupledsensor elements; and determining a button activation when the conductiveobject is detected on a first sensor element of the plurality of sensorelements using the individual capacitance measured on the first sensorelement.
 10. The method of claim 9, further comprising: performing afirst operation upon determining the first proximity event; performing asecond operation upon determining the second proximity event; andperforming a third operation upon determining the button activation. 11.The method of claim 10, wherein performing the first operation comprisesactivating a first portion of a display, wherein performing the secondoperation comprises activating a second portion of the display, andwherein performing the third operation comprises performing a buttonoperation.
 12. An apparatus, comprising: a plurality of sensor elements;a processing device, wherein the plurality of sensor elements areindividually coupled to the processing device to detect a presence of aconductive object on the apparatus, and wherein a group of sensorelements of the plurality of sensor elements are collectively coupled tothe processing device while the processing device is configured to applya signal to the collectively coupled group of sensor elements to measurea single collective capacitance for the group of sensor elements and todetect a presence of a conductive object in proximity to the apparatus;and a ground conductor, wherein the ground conductor is conductivelycoupled to the group of coupled sensor elements when the processingdevice is configured to detect the presence of the conductive object inproximity to the apparatus.
 13. The apparatus of claim 12, wherein theground conductor is coupled to a ground of the processing device whenthe processing device is configured to detect the presence of theconductive object on the apparatus.
 14. The apparatus of claim 13,wherein the ground conductor is a ground plane disposed to surround eachof the plurality of sensor elements.
 15. The apparatus of claim 13,wherein the ground conductor is conductive material of a housing of theapparatus.
 16. The apparatus of claim 13, further comprising a selectioncircuit coupled the processing device, wherein the selection circuit isconfigured to individually couple the processing device to each of theplurality of sensor elements in a first mode and to collectively couplethe processing device to the group of sensor elements and the groundconductor in a second mode.
 17. The apparatus of claim 16, wherein thegroup of sensor elements comprises all of the plurality of sensorelements or a fraction of all of the plurality of sensor elements. 18.The apparatus of claim 16, wherein the processing device is configuredto perform a single capacitance measurement on the group of sensorelements during each sensing interval when in the second mode, andwherein the processing device is configured to perform a capacitancemeasurement on each of the plurality of sensor elements during eachsensing interval when in the first mode.
 19. The apparatus of claim 12,wherein the processing device is configured to determine a buttonactivation when the conductive object is detected on a first sensorelement of the plurality of sensor elements, and wherein the processingdevice is configured to determine a proximity event when the conductiveobject is detected in proximity to the apparatus.
 20. The apparatus ofclaim 19, wherein each of the plurality of sensor elements correspondsto a button on a touch panel display, wherein the touch panel display isactivated when the proximity event is detected, and wherein theprocessing device is configured to perform a button operation thatcorresponds to the button that has been activated.
 21. The apparatus ofclaim 12, wherein the processing device and the plurality of sensorelements reside in a remote control device, and wherein each of theplurality of sensor elements correspond to a button on the remotecontrol device.
 22. The apparatus of claim 12, wherein the processingdevice and the plurality of sensor elements reside in at least one of atouch panel of a plurality of touch-sensor buttons, a touch-sensorslider, or a touch-sensor pad.
 23. An apparatus, comprising: a pluralityof sensor elements of a device; means for detecting a presence of aconductive object both on the device and in proximity to the devicebased on applying a signal to the group of coupled sensor elements tomeasure a single collective capacitance for the plurality of sensorelements and without using an additional proximity sensor; and means forconductively coupling a ground conductor to the group of coupled sensorelements to detect the presence of the conductive object in proximity tothe device.
 24. The apparatus of claim 23, further comprising means forcoupling a group of sensor elements of the plurality of sensor elementstogether, and wherein the means for detecting comprise: means fordetecting the presence of the conductive object in proximity to thedevice while the group of sensor elements are coupled together; andmeans for detecting the presence of the conductive object on the devicewhile the plurality of sensor elements are not coupled together.
 25. Theapparatus of claim 23, further comprising means for reducing powerconsumption of the apparatus.